Soft Scale Insects - Their Biology, Natural Enemies and Control Y. Ben-Dov and C.J. Hodgson (Editors) 9 1997 Elsevier Science B.V. All rights reserved.
1 . 2 . 3 . 2 The Pela Wax Scale and Commercial Wax Production TING-KU! QIN
INTRODUCTION Scale insects usually protect themselves by secreting wax to cover their bodies. In the family Coccidae, many species produce a large quantity of wax either covering their body or as an ovisac to protect their eggs. Some species of soft scales are regarded as beneficial because they produce wax useful to humans. In particular, the wax produced by the male nymphs of Ericerus pela (Chavannes) and the adult females of some species of Ceroplastes Gray have been utilised for many purposes. This Section deals mainly with wax production by E. pela since it is the only soft scale being used successfully in commercial wax production. However, the wax production of some species of Ceroplastes are also briefly discussed. Ericerus pela has been known by at least ten English names, e. g. wax-producing coccid (Sasaki, 1904), Chinese white wax scale (Kuwana, 1923; Wu, 1980a, b), Chinese wax scale (Essig, 1942), white wax scale (e.g. Wu and Zhoug, 1983; Jiang et al., 1984; Wu, 1987; Wu et al., 1988; Wu and Gao, 1990; Zhao and Wu, 1990; Wu et al., 1991), white wax insect (e.g. Zhang et al., 1990), China wax scale insect (Li, 1985), prototype wax scale (Brown, 1975), wax insects (Chou, 1990), Chinese scale insect (Waku and Foldi, 1984), and pela insect (Zhang, 1984). Some of these names can be confused with those of other species of wax scales, such as white wax scale for Ceroplastes destructor Newstead (e.g. Beattie et al., 1990) and Chinese wax scale for C. sinensis Del Guercio (e.g. Gimpel et al., 1974; Beattie et al., 1990). In order to avoid further confusion, "Pela wax scale" is used in this Section. "Pela" is a pronunciation of Chinese word meaning "white wax'. Moreover, this name relates to both the colloquial and scientific names. The commercial product of the wax produced by E. pela has been widely known as "China wax" outside China (e.g. Chiao and Pen, 1940; 1943; Takahashi and Nomura, 1982; Li, 1985) although there are other local names inside China (Wu, 1989). Therefore, the term "China wax" is employed here for the commercial product of E. pela wax.
HISTORY AND STUDY OF PELA WAX SCALE Ericerus pela is one of the oldest beneficial insects (after silk worms and honeybees) recognised by humans, having been reared for its wax for more than a thousand years. In China, it was recorded that in the Tang dynasty (618-907 A.D.) local governors offered China wax as a special gift to the emperor (Zou, 1981, see Li, 1985). This
Section 18.104.22.168 references, p. 319
Soft scales as beneficialinsects suggests that the rearing of E. pela in China is at least as old as the Tang dynasty. However, the earliest detailed records of breeding are from the Song dynasty (960-1279 A.D.) (Chou, 1990). During the Ming dynasty (1368-1644 A.D.), the insects were reared and studied in great detail in several important works (e.g. Wang, 1566; Li, 1578; Xu, 1639; see Chou,1990). These authors also discussed the different species of host plants, the distribution and habitats of the insects and the methods of collecting and processing the wax. N. Trigault, a Christian missionary, was the first European to observe the pela wax scale and wrote about wax collection in southern China in 1651 (see Chou, 1990). The news about pela wax scale spread to Europe in the eighteenth century. In 1847, this wax scale was recorded as a new species by Chavannes, who named it Coccus pela according to the pronunciation of the Chinese name "pela'. Lockhat sent samples of China wax and the pela wax scale to England from Shanghai for research in 1853, and Lichtoffen learned the techniques of collecting China wax in Sichuan in 1872 and recorded it in his travel letters (see Chou, 1990). Extensive literature is available on different aspects of E. pela and its wax production, including a number of books (e.g. Xu, 1959; Shaanxi Province Biological Resource Survey Team, 1974; Wang, 1978; Wu, 1989). Research on E. pela is still carried out in various parts of China but the three main research centres are: the Department of Biology, Sichuan University, Chengdu (led by Wu Ci-Bing and Zhong Yuan-Hui), the Southwest Agricultural University, Chongqing (led by Wang Fu), and the Shaanxi Institute of Zoology, Shaanxi (led by Zhang Zi-You and Shao Meng-Ming). The research at Sichuan University has been expanding to many new areas, including the measures needed to increase wax production (Wu, 1981), bionomics (Wu and Zhong, 1983), use of hybrid vigour (Wu, 1987), comparative studies of economic characters from different regions (Wu et al., 1988), male wax glands (Tan and Zhong, 1989), male reproductive system (Wu and Gao, 1990), female neurosecretory system (Peng and Zhong, 1990) and a study of embryonic development (Zhao and Wu, 1990).
BIOLOGY OF PELA WAX SCALE Geographical distribution The Pela wax scale is native to China and has been recorded from 18 provinces (Fig. 22.214.171.124.1). Wang (1963) suggested that E. pela was confined to 26-33 ~ N and that the most suitable region was between 26-29 ~ N. However, Wu (1980a, 1989) disputed Wang's (1963) statements and indicated a wider range from 23044 ' N to 41~ N, 85008 ' E to 121~ E (actually 124035 , E in Benxi, Liaoning province, according to Wu (1989)), and from almost sea level to 2800 metres altitude. In this area, the temperature ranges from -30.4 ~ to 44 ~ indicating that the insects are adapted to a broad range of climatic conditions. Wu's conclusions are supported by Zhang et al. (1986) who recorded natural populations of E. pela at Yongde county, Yunnan, which extends to south of 24 ~ N latitude. Zhang et al. (1990) claimed that the E. pela population occurring in the lower reaches of Jinshajing River, a contiguous area to Yunnan, Sichuan and Guizhou provinces, produced more eggs, had a higher male egg sex ratio, a longer wax-secreting period, a higher wax-producing capacity and therefore higher outputs of wax. Sasaki (1904) considered that E. pela was also native to Japan. Recently, the insect has been recorded from the Primorye Territory of Russia (Danzig, 1965) and from Korea (Paik, 1978). Some authors (e.g. Takahashi and Nomura, 1982; Wu, 1989) have mentioned that E. pela occurs in Europe; but no specific European countries have ever been given.
Fig. 126.96.36.199.1. Distribution of Ericeruspela in China. Betweendashed lines: general distribution; Diagonal shading: main region of wax production (Sichuan); horizontal shading: some wax production; black dots: west-, east-, north- and south-most recorded distributions; triangles: distribution in countries other than China. Commercial wax production regions in China China wax is produced mainly in Sichuan province but also in Hunan, Yunnan, Guizhou, Zhejiang, Shaanxi and Shanxi provinces (Fig. 188.8.131.52.1). Historically wax (males) and "seed" (females) production, occurred in separate regions and so males and females were considered to have different ecological requirements (Wang, 1963, 1978). However, Wu (1980a, 1980b) argued that, in order to reproduce successfully, males and females of E. pela should have the same ecological requirements (e.g. climate and host plants) and stated that both the seed and the wax could be produced in the same environments. The historical separation of wax and seed production regions is due to the different purposes of the production. Wu's statements were confirmed by Zhang (1984) who found that the commercial China wax could also be produced in the subtropical regions of Yunnan. Life cycle of pela wax scale In traditional areas of China wax production, E. pela has one annual generation (Fig. 184.108.40.206.2). However, in the subtropical region (Jingdong, Yunnan province), Zhang (1984) found that E. pela only need 10 or 10.5 months to finish a generation. Danzig (1965) noticed that E. pela needed two years to complete one life cycle in southern Primorye, Far East Russia. After analysing the ecological factors affecting the distribution of E. pela, Ke (1981) suggested that this insect may complete two generations annually in the tropics, one generation in the subtropics and a half generation in cold temperate regions.
Section 220.127.116.11 references, p. 319
Soft scales as beneficial insects
Fig. 18.104.22.168.2. Life cycle of Ericerus pela. E: eggs; FI: first-instar female; F2: second-instar female; MI: first-instar male; M2: second-instar male; M3: prepupa; M4: pupa; MS: adult male.
General biology The biology of E. pela has been studied in the univoltine regions by many authors (e.g. Sasaki, 1904; Kuwana, 1923; Chiao and Peng, 1943; Wang, 1963; Cheng, 1974; Zhang and Shao, 1982; Wu and Zhong, 1983; Zhang, 1984; Li, 1985; Wu, 1989). The following description of the life cycle is mainly based on the studies by Cheng (1974), Wu and Zhong (1983) and Wu (1989). The females of E. pela pass through three life stages: first- and second-instar nymphs and adult female; and the males through five stages: first- and second-instar nymphs, prepupa, pupa and adult male. Many soft scale species have three immature stages in the female but E. pela only has two.
i. Egg laying and hatching After overwintering, the fertilised females start laying eggs from as early as the beginning of February to as late as the middle of May in some regions. The number of eggs laid by each female varies greatly depending on the size of the female, ranging from 3,372 (Kuwana, 1923) to 18,047 (Wu and Zhong, 1983). The eggs take 20-34 days to develop. The newly hatched nymphs are pale, soft and feeble, and remain under the female body, but after about 5 days they have become hard and active and are ready to crawl out.
ii. First-instar nymph The yellow or red brown female nymphs become very active and emerge from beneath the female body. They wander on the branches first and then crawl towards a leaf and settle on the upper surface along the veins but do not congregate in groups. They feed there for a half to one month without moving, and this period is called "fixing leaves" or Ding Ye in Chinese. The hatching and emergence of the yellow-white male nymphs is always several days later than the females (usually 2-4, occasionally 6-11). Their behaviour differs from that of female nymphs in that, instead of settling on the upper surface of leaves, they congregate on the under surface and feed there for only two weeks.
iii. Second-instar nymphs and subsequent stages After the first moult, the second-instar females move from the leaves and settle on 2-3 year-old branches. This is called "fixing stems (Ding Gan in Chinese)" or "fixing branches". The head faces downwards and the abdomen upwards. After the second moult, the adult females appear in late August or September. The second-instar males migrate from the leaves to 2-3 year-old branches and settle, congregating around the branch. In contrast to the female, the head of male faces upwards. Males settle on the leaves after the females but appear on the branches before them. In late August to early September, second-instar males moult into prepupae and stop secreting wax. They become pupae 3-5 days later and the adult males emerge after another 4-8 days. Two to three days after emergence, the males fly off in search of adult females with which to mate. They die shortly afterwards. Males usually live for only 2-5 days. iv. Overwintering After mating, the body of the adult female only gradually enlarges until the following February, but then swells drastically, and when it reaches a length of 3 ram, the body starts to secrete sweet-scented drops (probably honeydew) (Diao Tang in Chinese) (Li, 1985, fig. 4), eventually becoming ball-like and reaching 8-10 (some 14) mm in diameter. The female then begin to lay eggs. Egg-laying lasts for about 10 days and the sweet-scented drops disappear. The eggs are deposited in a cavity beneath the female body. v. Sex ratio The sex of E. pela can be distinguished at every stage including eggs (male egg: pale yellow; female egg: slightly brownish). The sex ratio directly affects wax yields: the more males, the more wax. The sex ratio varies in different populations among the progeny of adult females of different sizes and from different host plants (Wu and Zhong, 1983; Wu, 1989; Zhang et al., 1990). Wu (1989) observed that the ratio of hatching nymphs is usually between 1" 1 and 5" 1 male to female with some extremes (0.12:1 or 6.1:1). Zhang et al. (1990) studied the egg sex ratio of populations from the main wax-production regions (Sichuan, Yunnan and Guizhou) and found that the highest male to female egg sex ratio was from Yunnan province (average 2.23:1, range between 0.25:1 and 22.27:1). vi. Host plants Pela wax scale has been recorded on about 40 species and subspecies of host plants (Table 22.214.171.124.1) mostly in two genera of the family Oleaceae. However, only ash, Fraxinus chinensis Roxb., and privet, Ligustrum lucidum Ait., are widely used to produce China wax, although L. quiboni Carr., L. acutissimum Koehnen and L. compactum Hook are also used in some parts of China. Natural enemies Wu (1989) reviewed information on the natural enemies of E. pela and its host plants and provided advice on their control.
i. Natural enemies of Ericerus pela Several groups of organisms have been reported to attack pela wax scale and these include parasitoid wasps, weevils, coccinellids, bagworm moths, spiders, birds and
Section 126.96.36.199 references, p. 319
Soft scales as beneficial insects
fungi. The parasitoid wasps and the weevils are widespread and are probably the most important natural enemies.
TABLE 188.8.131.52.1 Host plants of Ericerus pela (Chavannes). m_ Species names follow the spelling in "Index Kewensis"; names spelt differently by the original authors; b _ names not found in "Index Kewensis"; " - host plants widely used for wax production. "
Host plants #
Oieaceae Chionanthus retusa Lindl. & Paxt.' Fraxinus americana Lima. F. bungeana DC. F. bungeana pubinervis Wangeuh. F. chinensis Roxb.* F. chinensis rhynchophylla (Hance)" F. griflithii C.B. Clarke F. hopeiensis Tang F. longicuspis Sieb & Zucc. F. mandschurica Rupr." F. mariesii Hook.f. F. platypoda Oliv. F. paxiana Lingelsh. F. pubinervis BI. F. retusa Champ. F. sinensis [?=chinensis] b Ligustrum acutissimum Koehne L. amurense Cart." L. compactum Hook.f &Thoms. ~ L. delavayanum Harlot. L. glabrum b L. henryi Hemsl. L. ibota Sieb. L. japonicum Thunb. L. lucidum Ait.* L. medium Franch. &Sav. L. obtusifolium Sieb. &Zucc. L. quiboni Carr. L. robustum BI. L. sinense Lour." L. sinense nitidum Rehd. L. sinense stantonii Rehd. Syringa josikaea Jacq.f. Anacardiaceae Rhus succedanea Lima." Aquifoliaceae llex sp. Celastraceae Celastrus ceriferus b Malvaceae Hibiscus syriacus Linn. Verbenaceae Vitex sp.
Kuwana, 1923; Danzig, 1965 Wu, 1989 Cheng, 1974; Wu, 1989 Kuwana,1923 Cheng, 1974; Wu, 1989 Danzig, 1965; Cheng, 1974; Wu, 1989 Wu, 1989 Wu, 1989 Kuwana, 1923; Danzig, 1965 Wu, 1989; Danzig, 1965 Cheng, 1974; Wu, 1989 Wu, 1989 Wu, 1989 Sasaki, 1904 Wu, 1989 Blanchard, 1883 Cheng, 1974; Wu, 1989 Danzig, 1965 Wu, 1989 Cheng, 1974; Wu, 1989 Blanchard, 1883 Wu, 1989 Sasaki, 1904; Kuwana, 1923 Sasaki, 1904; Wu, 1989 Blanchard, 1883; Cheng, 1974; Wu, 1989 Kuwana, 1923; Danzig, 1965 Wu, 1989 Cheng, 1974; Wu, 1989 Cheng, 1974; Wu, 1989 Cheng, 1974; Wu, 1989 Cheng, 1974 Cheng, 1974 Danzig, 1965 Blanchard, 1883; Danzig, 1965 Tang, 1991 Blanchard, 1883 Blanchard, 1883 Danzig, 1965
(a) Wasps: Pela wax scale is host to 13 species of parasitoids (Wu, 1989), of which three are important: Microterys ericeri Ishii, M. sinicus Jiang and Tetrastichus sp. Jiang et al. (1984) studied the morphology, biology and control of M. ericeri and found that the wasp had 6-7 generations per year. The parasitoid larvae overwinter in the female scale, and the adults emerge and lay their eggs inside both female and male scales. Up to 45.3 % of males and 52.8 % of females of E. pela can be parasitised. (b) Weevil: the weevil, Anthribus lajievorus Chao, occurs in every wax production region. The adults bite the cuticle of the scale and fee~ on the body fluid. They lay their eggs inside the body after biting a hole and, upon hatching, the larvae eat the
scale's eggs. Anonymous (1976) studied this weevil in detail and found that up to 95.2 % of E. pela could be damaged by the weevil. (c) Coccinellids: two species of coccinellids: Chilocorus kuwanae Silvestri and C. rubidus Hope prey on the scale, but only the latter is important and specialises in preying on the male scales. There is one generation a year and each beetle can eat 10-13 thousand male scales during its life (Wu, 1980c; 1989). (d) Bagworm moths: apart from feeding on the host plants of E. pela, many bagworms also prey on the wax and the enveloped males. The important bagworms are Cryptothelea minuscula Bulter and C. variegata Snellen (Psychidae) (Wu, 1989). (e) Spiders: many spiders spin their webs on the host plants. These webs can trap the adult males when they are flying in search of mates (Cheng, 1974). (f) Birds and rodents: during the sweet-scented drop (probably honeydew production) period, rodents and many birds such as Phoenicrurus auroreus Pallas, Parus major Linnaeus and Pycnonotus sinensis (Gmelin) feed on the female scales (Cheng, 1974). Bird damage can reach up to 91.8% (Wu, 1989). (g) Fungi: Gloesporium sp. causes death of the females of E. pela; 40-83 % of the insects can be infected (Wu, 1989).
ii. Natural enemies of the host plants Apart from natural enemies feeding directly on E. pela, many other organisms can seriously damage the host plants, thus reducing wax production. Moreover, some natural enemies feed on both the insects and the plants (e.g. bagworm moths). Wu (1989) listed 19 species of insect pests belonging to the orders Lepidoptera, Coleoptera, Hemiptera, Orthoptera and Hymenoptera. The most important pests of the host plants varied between regions and between seasons but the armoured scale Pseudaulacaspis pentagona (Targioni Tozzetti) (Diaspididae), the sawfly Macrophya fraxina Zhow & Huang (Tenthredinidae) and the fraxinus aphid Prociphilus fraxini (Fabricius) (Aphididae) are among the most important ones.
Wax secretion and wax glands 1. Wax secretion Females: the wax secreted by the females is of no economic value. First- and second-instar females only secrete a small amount of wax from the spiracular pores, while the adult females secrete a thin layer of wax from tubular ducts on the dorsum and a small amount of white wax from the tubular ducts, multilocular disc-pores and spiracular disc-pores on the venter. Males: the first-instar males start secreting wax filaments 2 to 3 days after "fixing leaves". The wax covers the whole body after 6 or 7 days, although this layer is thin and of no economic value. The useful wax is produced by second-instar males. The density of the fixing area is about 200 individuals per square centimeter and the length of the settling area is 1-1.5 metres. Two to three days after "fixing branches", the male nymphs begin to produce wax filaments (Figs 184.108.40.206.3. A, B). The wax is secreted from the wax glands (details below) associated with tubular ducts (Fig. 220.127.116.11.3. C) on the dorsal and ventral surfaces (Fig. 18.104.22.168.2, M2). Initially, very little wax is secreted, but as the body grows, more and more wax is produced. Eventually, the wax is from 5-10 mm in thickness and entirely envelops the whole aggregation of insects and their branches (Fig. 22.214.171.124.4. A). This is called "wax flowers'. After the moult to the prepupa, wax
Section 126.96.36.199 references, p. 319
Soft scales as beneficial insects
secretion nearly stops. The prepupae, pupae and adult males produce only small amounts of wax. Wu (1989) indicated that second-instar males begin to secrete wax each day at 10 am, with peak daily secretion between 12 noon and 11 pm, and then gradually decreasing.
2. Number and structure of wax glands in the male Tan and Zhong (1989) studied in detail the wax glands in each stage of the male. The wax glands develop from specialised epidermal cells. There are few glands in the first instar but the number gradually increases as the insects grow. The second instar has the highest number of wax glands (about 300), which mature, secrete wax and then degenerate. There are extremely few wax glands in the prepupae. Pupae have no wax glands but a glandular pouch develops on each side of the base of the penial sheath, and each glandular pouch contains a long seta arising from its base (Giliomee, 1967). There are many pygidial gland units (Tan and Zhong, 1989) in each glandular pouch, and these glands mature and secrete a waxy substance which slides along the setae and forms the 2 conspicuous long waxy filaments (4-6 mm) of the living adult male (Giliomee, 1967; Tan and Zhong, 1989) (Fig. 188.8.131.52.2, M5; Fig. 184.108.40.206.4. B). A wax gland of a male nymph consists of a central cell, 3-5 (usually 4) lateral cells, 2 canal cells, a duct with an inner ductule and a terminal knob (Tan and Zhong, 1989, fig.4 [but terminology following Foldi, 1991]). Noirot and Quennedey (1974) divided the gland cells of insects into three classes and Tan and Zhong (1989) regarded the gland cells of E. pela as belonging to class 3, i.e. the canal cell secretes a cuticle canal which penetrates the gland cell and opens to the outside (Noirot and Quennedey, 1974, Fig. 3; Waku and Foldi, 1984). Foldi (1991) recognised five types of wax glands in scale insects and the wax gland of E. pela can be classified into his type 2 (Foldi, 1991, Fig. 2), which he called ducted wax glands. 3. Wax secretion periods in the second-instar male Tan and Zhong (1989) studied the development of the wax glands in the second-instar male nymphs, because the most useful wax is produced by this stage. They recognised five periods with two peaks of secretion: Period I (starting from "fixing branches" and lasting about 25 days): the number and size of the wax glands increase during this period. The average growth of dorsal glands is 0.8-2. l#m/day and that of ventral glands is 1.25~tm/day. The diameter of a dorsal gland ranges from 7.5-37.5#m; that of a ventral gland is 12.5-25.0#m. Mature wax glands are mostly on the dorsolateral parts of the body. Period II (days 25-35): the first peak of wax production occurs in this period, mainly by the dorsal wax glands. The thickness of the wax secretion increases from 0.3 #m/10 days to 1.3 #m/10 days. Most dorsal wax glands then stop growing and the ventral wax glands grow slightly (0.3#m/day) at the end of this period. Period III (days 35-65): at the beginning of this period, some wax glands continue to grow and secrete wax, although those that have already secreted wax begin to degenerate and disintegrate. Period IV (days 65-75): during this period, the second peak of wax secretion takes place, with the secretion being produced by the regenerated wax glands mostly located on the abdomen (at a rate of 1.4#m/day increase in diameter). The wax deposition increases from 0.5 #m/10 days to 1.4 #m/10 days. The number of the wax glands is smaller than in period II but there are more oenocytes around the wax glands and this suggests that the oenocytes probably play an important role in the biosynthesis of the wax.
Period V (days 75-85): most of the wax glands degenerate and only some newly developed glands still grow.
Fig. 220.127.116.11.3. Ericerus pela (Chavannes), male second instar. A - Scanning electron micrograph of the wax filaments produced by the second-instar male, showing numerous broken wax filaments; scale line: 10 Ira1. B - Scanning electron micrograph of the wax filaments (each 5-6 #m in diameter) produced by the second instar male; enlargements of several wax filaments; note the two types of filaments - smooth surface and longitudinally ridged surface; scale line: 5 #m. C - Tubular duct (13-16 #m long, 5-7 #m in diameter) of the second-instar male. A wax filament is secreted through this tubular duct to the cuticular surface; scale line: 5 #m.
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SoJ~ scales as beneficial insects
PRODUCTION OF PELA WAX SCALE AND ITS WAX "In the production of E. pela and its wax, the insects are the key, the trees are fundamental and the wax is the goal or objective" (Wu, 1989, p. 115). A sophisticated procedure has been developed during the long history of its cultivation. The methods are generally labour intensive. Many key steps have been summarised as easily remembered jingles, such as the one cited above. This section will outline briefly the methods of breeding E. pela for the purpose of wax production.
Seed production The following is mainly after Wu (1989): the females do not produce useful wax but they provide the source of the insects and are thus called " s e ~ ' . The place where the seed is produced is called the "seed source" (Chong Qu) and the place where the wax is produced is called the "wax source" (La Qu). The ~ source and the wax source should be separated in different fields (preferably in the same area to avoid long distance transportation) because the natural enemies in seed sources may continue to attack pela wax scale in wax sources if these are in the same field. In April and May, overwintered seeds (females with eggs, also termed "egg capsules" below) are collected from the fields (Li, 1985, Fig. 5). There are criteria to determine if the seed females are ready to be collected: the colour (red brown), the flexibility (when pushing the dorsum of the body, the touched areas should return to the original position) and the dryness (the body becomes dry). The collected seed insects need to be kept in cool, dry conditions until the egg capsules become hard. Then, large egg capsules which contain large numbers of eggs are selected for establishing new cultures. Once most female nymphs have hatched and some have crawled onto the surface of the egg capsules, they are ready to be wrapped in small bags (3-6 egg capsules per bag) and this process is called "wrapping insects" (Bao Chong in Chinese). When some female nymphs are found moving on the surface of the bags, the bags are hung on the appropriately pruned host plants and this is called "hanging bags" (Gua Bao in Chinese). After the crawlers have been released, care is needed in controlling natural enemies and in cultivating the host plants until the next generation of s e ~ is ready to be collected. These seed females are used for two purposes: either as a source for the next production (i.e. females) or as a source of males for wax production. The exposure of the seed to neutrons produced by decay of Americium-Beryllium (dose = 1 X 104n/cm2, 1 X 105n/cm2 or 1 X 106n/cm2) can significantly increase the wax production. Wu (1989) reported that the exposure of seed to the above three doses of neutrons resulted in an 11-38 % increase in average wax yield. Historically, the wax sources and the s e ~ sources are widely separated, even in different provinces. Therefore, it is necessary to transport the ~ from the source to the wax source. After the seed insects are picked from the trees, they are allowed to dry before packing. They are then packed in a linen or paper bag (about 30 x 24 cm) of gross weight 1.5 kg. The packed bags are transported by person, truck or aeroplane, depending on distance. Great care is required during transportation to avoid damage to the insects due to crowding and heating, and to avoid the nymphs from hatching too early.
Wax production 1. Release of male nymphs The seeds for wax production are kept indoors until the eggs hatch. The process of "wrapping insects" for the wax production is later than for the s e ~ production because the male crawlers always hatch after crawler female. The egg capsules are ready to be wrapped for the wax production when 80-90% of the yellow- or red-brown female crawlers appear on the outside of the shells and some yellow-white male crawlers begin to appear. Basically, the delay in wrapping insects allows the earlier-hatched females to die, so that only male crawlers are released onto the tree. There are two means of
determining the appropriate time for releasing the male crawlers" (1) random checking of several bags to see if most male crawlers have moved to the inside of the bag. If they have, they should be released immediately; and (2) hanging a couple of bags on a tree in the morning and if many male crawlers have crawled onto the tree and moved towards to the leaves at noon, the crawlers are ready to be released. If the crawlers remain around the bags, it means that they are not ready to be released. The egg capsules can be maintained at 18"C because the nymphs begin to hatch at above 15~ but are inactive below 180C, and so this allows the eggs to hatch but the nymphs do not move out of the shells. After all the nymphs have hatched, the bags can be hung on the trees at the same time so that all the crawlers can settle on leaves in a very short time, thus reducing the loss of insects during the process of "fixing leaves'. The time for "hanging bags" is usually in early May and the best position is from young branches near leaves because male crawlers are not as active as females, and once they leave the bag, they move up and immediately fix on leaves. 2. Post-release management Once the insect bags have been hung in the tree, the greatest threat is from storms which wash away the male nymphs. Therefore, during inclement weather, the bags are brought indoors and then hung out again after the storm. Management after release is summarised as follows: (1) examine the progress of "fixing leaves" and, if the leaves are too crowded, move some bags to another tree on which fewer insects are "fixing leaves'; (2) collect fallen leaves or bags and return them to the trees if they still have male nymphs; (3) monitor and control the natural enemies, for example, adult and larval coccinellids of C. rubidus; these are dislodged by hitting the tree regularly every 2-3 days using a stick and then killing the beetles on the ground; (4) fertilise the host trees to provide nutrients to encourage the males to produce more wax; (5) prune the flowering and newly developed branches because they consume plant resources which otherwise would be available to the scale. 3. Harvesting wax flower The Wax flower is the thick wax which completely envelops the aggregation of second-instar male nymphs and their branches (Fig. 22.214.171.124.4. A). When the wax surface is full of small holes with two long white waxy filaments extruding from each hole (Fang Jian in Chinese) (Fig. 126.96.36.199.4. B), the nymphs have become pupae and wax secretion has stopped. Once the first white filaments appear, the nymphs under the wax are checked and, if their body is pale yellow-brown with a black dorsum to the thorax, the wax flower is ready to be collected. If the insect's body has become brown, the wax flowers should be collected immediately because the males will emerge very soon. The quality and quantity of the wax may be reduced if collected too early or too late after male emergence. The wax can be collected easily when wet and therefore the most suitable weather for collection is light rain, or just after rain, or on a free morning before the dew has dried. If wax collection is done at noon or in the afternoon of a dry day, the wax should be sprayed with clean water before collection, otherwise part of the wax will remain on the tree or the wax will be easily broken and fall to the ground. There are two methods of collection: "cutting branches" or "leaving branches". If the branches are weak and have already been used twice, the wax-laden branches are cut down, and this allows new shoots to grow. If the branches have been used only once, they should still be strong and healthy, and should be left to rest for a year before being used again; in this case, the wax is scrapeA off and the branches are retained. Preferably the wax should be processed on the day of collection, but if not it should be stored in a cool and ventilated place to avoid heating.
Section 188.8.131.52 references, p. 319
Soft scales as beneficial insects
Fig. 184.108.40.206.4. Wax of Ericerus pela (Chavannes). A - Photograph of "wax flowers" enveloping the aggregated bodies of the second-instar males on a branch of privet tree; scale line: 10 mm. B - Illustration of wax aggregated on a branch (= "wax flower'). Arrows point to the protruding wax filaments secreted from the glandular pouches of the adult male; scale line: 10 mm.
CHEMICAL AND PHYSICAL PROPERTIES OF THE W A X
Chemical characteristics The chemical composition of the wax (unrefined or raw wax) has been investigated by several authors (e.g. Hashimoto and Mukai, 1967; Tamaki, 1970; Hashimoto and Kitaoka, 1971; Takahashi and Nomura; 1982). Using gas chromatography (GC) and gas chromatography-mass spectroscopy (GC-MS), Takahashi and Nomura (1982) confirmed the results by Hashimoto and Mukai (1967) that the main components of the wax produced by E. pela are wax esters (92.5 %) together with some other classes of lipids (hydrocarbons 0.8%, free alcohols 0.4%, free fatty acids 0.2% and unidentified compounds 4.1%). The identified components of the wax esters are C2s, C30 and C32 alcohols and the corresponding fatty acids, with an additional C~ acid. In addition, Wu (1989) mentioned that C27 alcohol and C27 fatty acid were also present. The most abundant of the wax esters is cerotyl cerotate, hexacosyl hexacosanoate (C25H51COOC26I-/53) (55.2 %), followed by hexacosyl tetracosanoate (22.4 %) and hexacosyl octacosanoate (16.7%), and these three components constitute 94.2% of the total crystalline wax secreted by E. pela. Takahashi and Nomura (1982) also analysed the constituents of the hydrocarbons and the free fatty acids using GC and/or GC-MS. They found that the hydrocarbon fraction of the crystalline wax was composed of n-hentriacontane (31.4%), n-nonacosane (28.7 %), n-tritriacontane (17.7 %), 3-methylnonacosane (9.5 %), n-heptacosane (5.0%), 3-methylheptacosane (3.7 %), methylpentatriacontane (3.0 %), n-pentatriacontane (2.7 %), n-pentacosane (1.3 %)and unidentified constituents (2.0 %)[percentage total greater than
100% but correctly cited from Takahashi and Nomura (1982, table 3)]. The free fatty acids after methylation are methyl oleate (40.4%), methyl stearate (34.3%), methyl palmitate (6.8 %), methyl myristate (4.1%), methyl archidate (1.4 %) and unidentified material (13.0 %). The analyses of both Hashimoto and Mukai (1967) and Takahashi and Nomura (1982) were based on wax collected from Ligustrum japonica Thumb. in Japan. In China, however, the wax is harvested mainly from L. lucidum brit. and Fraxinus chinensis Roxb. and its composition has not been studied in detail. Nevertheless, one would not expect the wax produced in China and Japan to be different since Brown (1975) stated that none of the chemical constituents of coccid waxes are directly derived from the host plants. Hashimoto and Mukai (1967) noticed that triglycerides and phospholipids are major components of the lipids in the body of the male pela wax scale but they were not detected in the wax secreted by the insects. Physical and chemical characteristics of refined wax Wu (1989) summarisexl the characters of refined China wax. It is white or slightly yellow with a soft and shiny surface and no odour. It is hard with a slight brittleness, and a broken section shows needle- or pellet-like crystals. China wax is not soluble in water, and only slightly soluble in alcohol and ether. It is soluble in organic solvents such as formalin, benzene, toluene, xylene, trichlorethylene, chloroform and petroleum ether. After analysing 60 samples of China wax from different wax-production regions in 1980, the China Wax Standard Working Group of the Ministry of Commerce of the People's Republic of China concluded that the physical and chemical constants for China wax (probably commercial products) were as follows: melting point = 82.9~ acid value = 0.7, saponification value = 79.5, iodine value = 4.1, water or vapour material = 0.09 % and non benzene soluble material at 15~ = 0.08 %. These constants are different from those listed by Hashimoto and Mukai (1967) who analysed the raw wax (=wax-shell) and found: melting point = 85.0-85.6 ~ acid value = 0.8, saponification value = 107.4 and iodine value = 0.3.
COMMERCIAL PRODUCTS OF CHINA WAX There are two classes of commercial products from China wax, i.e. semifinished wax and refined wax. The processing of these classes of wax is explained below.
Semifinished wax The wax may be processed by either boiling or steaming. Boiling is the traditional method and is still widely used. Steaming can produce better quality wax but requires a steamer which is usually too small, and hence is not widely employed in wax processing. 1. Boiling method First grade wax and "crusted wax"" wax flowers are boiled in water at a wax:water until all the wax has melted. The wax forms the top layer and into a mould, where it is left to solidify (Fig. 220.127.116.11.5). This is the first Finally, cold water is added to the boiler so that any remaining wax becomes wax is called "crusted wax".
Section 18.104.22.168 references, p. 319
ratio of 2" 1 is removed grade wax. solid. This
Soft scales as beneficial insects
Second grade wax: after the first grade wax and crusted wax are taken, the remaining bodies of male pupae are transferred to a large bamboo or wicker basket and washed with clean water until all yellow colour is removed. The washed remains are poured into a vat to soak, with a change of water 2-3 times a day for 2 days. The water is then drained and the remaining insect bodies are wrapped in a bag and boiled to obtain more wax. The wax is transferred to a container, boiled once more in the boiler, poured into a mould and cooled to solidify. This is the second grade wax.
2. Steaming method The difference between the steaming and boiling methods is in making the first grade wax. The processing of other grades of wax is the same. The wax flowers are steamed to allow the wax to melt and flow into the water but the insect bodies remain in the steamer. The melted wax is the first grade wax and the remains are used to make second or other grades of wax. Some buyers accept the above semi fmi shed wax but others only accept the refined wax (see below).
Refined wax The semifinished wax can be ref'med as "rice core wax" (Mi Xing La in Chinese) or "horse tooth wax" (Ma Ya La in Chinese). Rice core wax is produced by mixing different proportions of the first (50-70 %) and second (30-50%) grade wax. There are different methods of mixing these two grades of wax" either by using water and boiling or by melting the wax without water. These processes allow further refinement of the wax. Horse tooth wax is produced from all wax not suitable for making rice core wax. The method is the same as for making rice core wax and the intention is to further refine the wax.
The steaming method can also be used to make rice core wax and horse tooth wax. The wax produced using this method is better than that from the traditional boiling method.
Fig. 22.214.171.124.5. Stacks of wax cakes after processing, each weighing about 5 kilograms (from Li, 1985).
Uses of China wax China wax has been used as a candle-making material in China for centuries. It must have played a important role in people's lives before substitute waxes were discovered and before electricity was invented. However, it is still used now for many other purposes (Li, 1985; Wu, 1989). Industry: (1) because of its light, shiny, non-deformable characteristics and high accuracy in producing shapes, China wax is an ideal material for casting moulds, particularly in the manufacture of aeroplane instruments and in mechanical and precision instrument production; (2) it can be used for the insulation of cables, electrical equipment and insulated wires, and as an anti-corrosive coating on ammunition; (3) in the paper industry, China wax can be used as an ingredient of emulsified sizing preparations, for sizing high-gross paper, filling and shining agents in paper productions such as tracing paper, waxing paper, paper for coating sweets and for decorating fancy foods, etc.; (4) it is used as an ingredient in polishes for automobiles and tyres in the car industry, as a dressing ingredient, and in f'mishing preparations and various polishes such as shoe creams, pastes and polishes in the leather industry; as an ingredient in sizing, finishing, and waxing clothes and sewing thread in the textile industry; in the preparation of various inks and as modelling wax in teaching aids; (5) it is also used to polish furniture. Pharmacy and medicine: China wax has long been used in traditional medicine in China. Li (1578, see Wu, 1989, p. 4), who was a well known physician of the Ming Dynasty, summarises: "Pela (China wax) is lukewarm and non-poisonous, it can restore vital energy and stop bleeding, relieve pain and reinforce weakness, restore muscles and set broken bones; taking it as pills can kill worms; polishing the head can cure baldness". Some of the above statements made by Li (1578) may have no scientific basis but it shows that China wax has been used as traditional medicine for hundreds of years. It can be used by itself or as an ingredient with many other traditional medicines. Nowadays, the medicinal uses of China wax have been expanded to heal uterus epilepsy, pelvic infection, uterus atrophy, and for wound swelling, breach of skin, chronic gastritis and rheumatism (Wu, 1989). China wax is widely used in pharmaceutical production, e.g. in coating pills and for sealing medicine bottles to prevent the drugs from denaturing during storage. Agriculture and horticulture: China wax is used as a grafting agent in grafting fruit trees, to prevent desiccation and to stop rain water getting into graft cuttings and hence increase the success of grafting. The remaining material (pupae of the insects) after processing the wax is ideal food for pigs and other husbandry animals. In addition, China wax can be used to make imitation fruits and flowers. For most of the above uses, a number of other waxes can replace China wax. However, China wax has advantages over other waxes because its melting point (83-86 ~ is higher than that of many other waxes, such as the widely used paraffin wax (50-60~ Kuwana (1923, p. 405) predicted that "this interesting insect-wax [China wax] industry may at some future date become extinct'. However, although production has declined since the 1940's, China wax industry shows no signs of extinction and the wax is still being produced and widely used in China. Indeed, the production of China wax cannot now meet the increasing demand in areas such as in the paper and drug manufacturing industries. Moreover, production and use of China wax does not cause any contamination to the environment and increased demand for environmentally safe products will stimulate greater production of China wax.
Section 126.96.36.199 references, p. 319
Soft scales as beneficial insects
Yield of China wax There are apparently no statistics on the overall yield of China wax from China. All estimates of wax production probably apply only to Sichuan province--the main waxproducing region. Sasaki (1904) stated that the wax harvested in a year was 600,000 Chin (300 tons). Wilson (1913, see Kuwana, 1923) mentioned that 50,000 piculs (3,000 tons) of wax was an average production in a poor year but in a favourable year, the yield was more than double this figure. Chiao and Pen (1940) recorded that about 2,800 tons of China wax were produced annually in Sichuan. However, Wu (1989) stated that, since 1949, the highest annual production of China wax has been 590 tons and production has never fulfilled the great demand.
WAX PRODUCTION OF SPECIES OF CEROPLASTES The females of all species of the wax scales (subfamily Ceroplastinae) produce a thick layer of wax which covers the body. The wax composition of at least 9 species of Ceroplastes has been analysed (e.g. Gilby and Alexander, 1957; Broch6re and Polonsky, 1960; Faurot-Bouchet and Michel, 1965; Tamaki and Kawai, 1968; Tamaki et al., 1969; Hashimoto and Kitaoka, 1971; Rios et al., 1974; Naya et al., 1981; Pawlak et al., 1983). The chemical composition of the wax of the cover is discussed in Section 188.8.131.52. Blanchard (1883) recorded that the wax secreted by at least 8 species of Ceroplastes could be useful. In particular, the wax of C. ceriferus (Fabricius) has been used as medicine (Essig, 1942) and in candle production (Cotes, 1891) in India. J. Anderson (see Blanchard, 1883; Cotes, 1891) observed people in Madras eat the wax of C. ceriferus. Blanchard (1883) suggested that an industry might be established to process the wax of C. rusci (L.). Some species of Ceroplastes have been used for millenia for the production of wax in Central and South America (Brown, 1975). The Indians of the southwestern United States of America have used a similar wax product produced from the irregular wax scale, C. irregularis Cockerell, to water-proof or seal baskets and pottery (Essig, 1931).
CONCLUSION Although many soft scales produce wax, few provide wax useful to people. While some species of Ceroplastes are considered to be pests, the wax produced by females of other species has been utilised for centuries in India and Central and South America. However, to-date the most useful wax producer among the soft scales is E. pela. This species has been reared commercially in China for more than a thousand years. The wax produced by the second-instar males of this insect is composed mainly of wax esters together with small amounts of hydrocarbons, free alcohols and free fatty acids. The commercial product that is processed and refmed from this wax is widely known as China wax. Apart from use in traditional candle-making, China wax has many industrial applications. The China wax industry has declined since other waxes (especially paraffm wax) were discovered, but the melting point of China wax is higher than that of many other waxes and hence it is safer to use. Nowadays the production of China wax cannot meet the increasing demands. Moreover, the use and production of China wax is environmentally friendly.
ACKNOWLEDGEMENTS I thank Dr Jing Dao-Chiao of Guizhou Agricultural College, China, Professor Shozo Takahashi of Kyoto University, Japan, Dr Toshiya Hirowatari of University of Osaka Prefecture, Japan, and Dr Yair Ben-Dov of the Agricultural Research Organization, Israel, for providing me with literature; Mr Sueo Nakahara and Dr Douglass R. Miller of the United States Department of Agriculture, USA, for arranging the loan of material of E. pela, Professor Li Zi-Zhong, Mr Luo Lu-Yi, Mr Liu Zuo-Yi and Dr Jing DaoChiao of Guizhou, China, for collecting and sending me specimens of E. pela; Professor Tang Fang-De (=Tang Fang-teh) for checking page numbers of some references; Professor Li Chen-Kang for his permit to reproduce Figure 11 from Li (1985) in Fig. 184.108.40.206.5 of this Section; Dr Chris Reid for help in translation of French text; Dr Pete Cranston for ideas on the structure of this paper; Dr Jonathan Banks for reading the section on chemical composition and chemical characteristics of the wax; Dr Bruce Halliday for reading and commenting on the manuscript; the Electron Microscopy Unit at the Australian National University (ANU) for facilities and assistance with the SEM micrography; and Mr Keith Herbert of the Division of Botany and Zoology, ANU, for reproducing the photographs. My special thanks go to Dr Penny Gullan who helped me in many ways and especially for critically reviewing the text and correcting the English. The manuscript was improved by comments from the reviewers.
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