FNZ 66 - Diaspididae (Insecta: Hemiptera: Coccoidea) - Introduction
Henderson, RC 2011. Diaspididae (Insecta: Hemiptera: Coccoidea). Fauna of New Zealand 66, 275 pages.
( ISSN 0111-5383 (print), ISSN 1179-7193 (online) ; no. 66. ISBN 978-0-478-34726-5 (print), ISBN 978-0-478-34727-2 (online) ). Published 23 May 2011
The armoured scale insects (Sternorrhyncha: Coccoidea: Diaspididae) are sap-sucking hemipterans with some unique features compared with other scale insect family groups. For example, they possess a blind gut with no direct connection between the stomach and the anal opening, and thus they do not produce the sweet exudate known as honeydew. In mitigation, their bacteriomes contain vertically transmitted endosymbionts that aid synthesis of vital dietary components (e.g., amino acids) missing from the plant sap that they ingest (Gruwell et al. 2007; Andersen et al. 2010). Armoured scale insects are characterised by extremely reduced morphology in the larviform adult females (loss of legs, antennae reduced to unsegmented tubercles) (Balachowsky 1948; Takagi 1993). In their consequent sedentary lifestyle, they are protected by the specialised scale cover which is constructed from the cast nymphal skins combined with waxes produced from ducts and pores on the highly modified posterior abdomen, the pygidium. The Diaspididae is the largest family of the Coccoidea with more than 2460 diaspidid species currently known (Ben-Dov, ScaleNet, 2010; Miller & Gimpel, ScaleNet, 2010), and these are found in all landmasses of the world except the polar regions (Miller & Davidson 2005).
In the classification of the Diaspididae two main subfamilies, the Aspidiotinae (aspidiotines) and Diaspidinae (diaspidines) (see Fig. 2–4) are recognised, and most species can be assigned to one or the other (Miller & Davidson 2005). Subfamily morphological distinctions are useful for diagnosing species, although these assignments may be arbitrary rather than reflecting ancestry because molecular phylogenetic studies show that the subfamilies are not monophyletic: this is more the case with the Aspidiotinae than with the Diaspidinae (Andersen et al. 2010).
It seems that parts of the New Zealand fauna may have been lost through recent geological time, because notably just one endemic aspidiotine taxon remains here now (Aspidioides corokiae (Maskell)) among all the others which are diaspidines. By comparison, aspidiotines are relatively common among the adventive fauna (e.g., Aspidiotus nerii Bouché, Hemiberlesia spp., Lindingaspis rossi (Maskell)) (Henderson 2007). Aspidiotine scales were present in New Zealand in the Miocene, as shown by a well-preserved, 20-million-year-old, fossil of an extinct aspidiotine described by Harris et al. (2007), when the climate was warmer and plant assemblage more diverse (Gibbs 2006; Mildenhall 1989; Pocknall 1989; Pole 1993; Pole et al. 2003). After the Miocene period, plant assemblages changed dramatically in response to tectonic upheaval of the landmass and a cooling climate, while later glacial cycling over the past 5 million years has destroyed the fossil record of the Pleistocene and Pliocene (Gibbs 2006; Henderson 2007). Many of the at least 15 plant families and 36 genera lost from New Zealand since the Miocene are still represented in Australia and New Caledonia (Gibbs 2006; Lee et al. 2001). The loss of the wider range of host plants once available may explain why the New Zealand armoured scale insect fauna has become rather depauperate, with a mere 22% generic endemism (Henderson 2007), yet within this fauna are some polyphagous genera with wide host ranges (e.g., Fusilaspis, Poliaspis, and Symeria) and, notably, the species-rich Leucaspis with a putative 50 (mostly undescribed) species. Then there are surprising gaps: it is interesting to compare the absence of diaspidids on Nothofagus with the radiation of Nothofagus-feeding Eriococcidae in New Zealand (Hardy et al. 2008; Henderson 2007).
As noted in Fauna of New Zealand 41 (Hodgson & Henderson 2000), the New Zealand Coccoidea were first studied between 1879 and 1898 by W. M. Maskell who described about 300 species of Sternorrhyncha from around the world. The Diaspididae of New Zealand described by Maskell were a mix of adventive species that had arrived on exotic plants brought by early settlers, and endemic species discovered in the native forests. In 1887 Maskell summarised the Coccoidea in New Zealand as “insects noxious to agriculture and plants” and gave useful advice on their control to help farmers, orchardists, and gardeners defend their plants against the increasing prevalence of exotic pests in the new country (Maskell 1887). There was no mention then of protecting the natural environment for the benefit of the endemic species, none of which has subsequently become a pest of non-native plants.
The family Diaspididae in New Zealand has not received much taxonomic attention since Maskell’s time, apart from the following: Morrison redescribed Anoplaspis metrosideri (Maskell) and described A. maskelli (Morrison & Morrison, 1922); Green (1929) described some species and the genus Symeria from material sent to him from New Zealand by J. G. Myers; Borchsenius & Williams (1963) studied the type species of Aspidioides and Scrupulaspis and erected 2 new genera, Eulepidosaphes and Labidaspis (the latter a leucaspidine); further species were described in the tribe Leucaspidini (Brittin1915, 1937; de Boer & Valentine 1977). More recently Henderson clarified some synonymies in two brief papers (Henderson 2000, 2001), and Charles & Henderson (2002) produced a catalogue of exotic armoured scale insects with an annotated checklist, which usefully expunged 8 erroneous records for pest species. Since then, 2 new exotic species have become established, namely Carulaspis minima (Signoret) on conifers and Furchadaspis zamiae (Morgan) on cycads.
This revision updates the nomenclature of the Diaspididae (except Leucaspidini) in New Zealand. It has necessitated an overhaul of generic concepts of the endemic species, and introduces new names to reconcile some instances of taxonomic confusion. Molecular data (Andersen et al. 2010) show that the northern hemisphere Fioriniina (Fiorinia + Lineaspis + Pseudaulacaspis) is distinct from the southern Fioriniina (Poliaspis + southern “Chionaspis/Pseudaulacaspis”), hence new genera were required to solve these nomenclatural problems. In addition, Pinnaspis dysoxyli is not closely related to other Pinnaspis species (Andersen et al. 2010, Fig. 1). Descriptions of 4 new genera — Anzaspis, Pellucidaspis, Pseudodonaspis, and Serenaspis and 2 reinstated genera Fusilaspis and Symeria — and 7 new species bring the number of endemic species to 20 in 10 genera. In addition, there are 8 Australasian species in 6 genera, and 21 cosmopolitan adventive species in 14 genera, making a total of 49 species. Four of the Australasian species (Anzaspis angusta (Green), Pseudaulacaspis brimblecombei Williams, P. eugeniae (Maskell), and Trullifiorinia acaciae (Maskell)) and all the endemic species are provided with descriptions and figures of adult female, male and female 2nd-instar nymphs, and 1st-instar nymphs where available. The treatment of the other 4 Australasian species (Lepidosaphes multipora (Leonardi), Lindingaspis rossi (Maskell), Parlatoria fulleri Morrison, and P. pittospori (Maskell)) and all the cosmopolitan adventive species is limited to a diagnosis and figure based on the adult female alone. The tribe Leucaspidini is excluded here and will be revised in a future volume.
Chionaspis angusta Green and Pseudaulacaspis cordylinidis (Maskell) are transferred to Anzaspis n.gen.; Pseudaulacaspis phymatodidis (Maskell) is transferred back to an earlier combination as Fusilaspis phymatodidis (Maskell), and Pseudaulacaspis dubia (Maskell) is a new junior synonym of F. phymatodidis; Pseudaulacaspis epiphytidis (Maskell) becomes the senior synonym of Andaspis asteliae (Green) and is transferred to Pellucidaspis n.gen; Lepidosaphes lactea (Maskell) is transferred to Poliaspis Maskell and P. argentosis Brittin becomes a junior synonym of P. media Maskell; Natalaspis leptocarpi (Brittin) becomes Poliaspoides leptocarpi (Brittin), (Miller & Gimpel 2009; for a full discussion on the generic synonymy see Takagi, 1969, p. 58); Trullifiorinia minima (Maskell) becomes the senior synonym of Pinnaspis dysoxyli (Maskell) and is transferred to Serenaspis n.gen.; Scrupulaspis intermedia (Maskell) and Eulepidosaphes pyriformis (Maskell) are transferred to Symeria Green. In addition, Fiorinia drimydis (Maskell) is considered a nomen dubium because the only material available is 2nd-instar male nymphs of an unidentifiable Leucaspis species.
The adventive cosmopolitan pest species are well documented for purposes of New Zealand phytosanitary regulations. The national catalogue of exotic armoured scale insects (Charles & Henderson 2002) provides information on biosecurity obligations (Biosecurity Act 1993, Hazardous Substances and New Organisms Act 1996, and article 8h of the Convention on Biological Diversity). Heavy emphasis is placed on border control, and all new organisms are assumed to be a threat to native flora and fauna — even those imported as biocontrol agents — until, or if, their host specificity and potential economic benefit can be scientifically demonstrated (Charles & Henderson, 2002).
Natural enemies of armoured scales already present in New Zealand include hymenopteran parasitoids, Coccinellidae and mites, earwigs, lepidopteran larvae, and entomopathogenic fungi. Information on the parasitoids may be found in Valentine & Walker (1991) and the BCANZ website http://www.b3nz.org/bcanz/index.php (Ferguson et al. 2007). Coccinellid beetles in the genus Chilocorus were imported as biocontrol agents in tandem with Hemisarcoptes mites to control pest armoured scales in kiwifruit orchards, but the beetles failed to establish and without them to distribute the phoretic mites, the Hemisarcoptes populations are scarce (Hill et al. 1993; Charles et al. 1995). European earwigs, Forficula auricularia, were found to consume large, mature Hemiberlesia female scales in kiwifruit orchards but the total impact was low (Logan et al. 2007; Hill et al. 2005; Maher et al. 2006). The two entomopathogenic fungi present in New Zealand, Cosmopora (Nectria) aurantiicola (anamorph Fusarium larvarum) and C. (N.) flammea (anamorph F. coccophilum) are known to infest and kill populations of native and adventive scales in the wild (Fig. 46) (Tyson et al. 2005; Henderson 2004). In 2002 various samples of infected scales were collected from five localities to develop useful isolates for biocontrol in kiwifruit orchards (Tyson et al. 2005). Larvae of Batrachedra arenosella s.l. (Lepidoptera: Batrachedridae) have been reared from Anzaspis (as Pseudaulacaspis) cordylinidis (Maskell) on cabbage tree (R. J. B. Hoare, pers. comm.), and they commonly attack and destroy local populations of the flax scale, Poliaspis floccosa n.sp., on Phormium tenax.
Miller & Davidson (2005) provided an extensive outline for management of armoured scales and should be referred to for details. They mention an interesting observation in regard to control methods. They had monitored the scale populations on the University of Maryland campus over about 40 years and during the first half of that time, plants were regularly sprayed with insecticides to control various pests. The scale populations were plentiful then, an unintended result of the suppression of their natural enemies. In the later time, they note that those scale populations have practically disappeared since an integrated pest management system (IPM) has been implemented (Miller & Davidson 2005).
None of the endemic or Australasian species are of economic importance in New Zealand. Of the cosmopolitan species, Aspidiotus nerii, Hemiberlesia lataniae (Signoret), and H. rapax (Comstock) are problematic in kiwifruit orchards mainly because of nil-tolerance for export fruit. Aonidiella aurantii (Maskell) (California red scale) attacks leaves, fruit, and wood of Citrus and is common in the warmer parts of the North Island but is usually only a minor pest (Charles & Henderson 2002). Diaspidiotus ostreaeformis (Curtis) (oystershell scale), D. perniciosus (Comstock) (San José scale), and Lepidosaphes ulmi (Linnaeus) (apple mussel scale) are pests of pip and pome orchards: they are mainly found on the wood but in large populations can move to and damage the fruit (Charles & Henderson 2002). Lepidosaphes beckii (Newman) and L. pinnaeformis (Bouché) are not the serious pests here in New Zealand as they can be overseas (Charles & Henderson 2002). Parlatoria pittospori (mauve pittosporum scale) was a pest of apple orchards in the Nelson area until Timlin (1964a, 1964b) discovered that the commonly planted Pinus radiata shelter belts surrounding the affected orchards harboured reservoirs of the scale, from where crawlers were blown to the apple trees. None of the other adventive diaspidids are currently of economic importance.
McClure (1990) remarked on the profound effects of host plants on the morphology and phenology of armoured scale insects, noting that this has at times caused much confusion among systematists. One of the classic examples is a species with leaf and bark forms mistakenly described as two species in two different genera, Chionaspis sylvatica and Phenacaspis nyssae. Although the median lobes of each form are strikingly different, intermediate forms were found within the same colony and the species were synonymised by Takagi & Kawai (1967). Further careful host transfer experiments unconditionally corroborated the finding (Knipscher et al. 1976). The evolution of such dimorphism in armoured scale insects with a bark (or winter) form and a leaf (or summer) form is, of course, related to their deciduous host trees, and so is of less consequence in New Zealand’s evergreen forests. Bark and leaf forms may be found among some undescribed New Zealand Leucaspis species (unpublished data), but as these are on evergreen trees they appear to be unrelated to the deciduous host tree effect.
The speciation process can be considered in regard to distinct host races or demes, which are reproductively isolated in time and space, and the effects of host plants on morphology and phenology (McClure 1990). Where there is uncertainty concerning species boundaries for a polymorphic species on different host plants, that species might represent a number of cryptic species. In this study it has been decided to retain Poliaspis media Maskell as a species complex because of these difficulties. Similarly, Symeria pyriformis (Maskell) is so polyphagous that it might be in the process of speciation in any number of host plant associations. Where morphological features were found that could be clearly tested in keys, this was considered sufficient distinction to treat an entity as a species, and so far three species closely related to S. pyriformis have been described. Often the taxon was associated with a particular host plant. A fourth possible species was investigated in association with the native podocarp, rimu, Dacrydium cupressinum (Henderson 2004). When S. pyriformis colonises rimu trees, the 1st-instar nymphs develop extraordinary groups of wax-producing head ducts (see Fig. 114–117). It is considered a case of host plant resistance, whereby the plant compounds ingested by the female scale impact directly on embryogenesis to cause the multiplication of head ducts (Henderson 2004). In kiwifruit orchards much effort goes into controlling pest scale insects without the use of harmful pesticides, and recent studies have demonstrated host resistance to H. lataniae by some cultivars of Actinidia species (Hill et al. 2009; Hill et al. 2010).
Among the few strictly monophagous diaspidid species in New Zealand, a good example is Poliaspoides leptocarpi (Brittin) on oioi, Apodasmia similis (Restionaceae). Some of the species closely related to Poliaspis media and Symeria pyriformis have developed specificity on narrow host preferences, e.g., Poliaspis chathamica n.sp. on Olearia traversii, and further examples named for their respective host plants are P. salicornicola n. sp., P. raouliae n. sp., Symeria phyllocladi n. sp., and S. leptospermi (Maskell). Anzaspis gahniae n. sp. is restricted to Gahnia species (Cyperaceae). Pseudodonaspis mollyae n. sp. feeds on Poa and Chionochloa species (Poaceae). Anoplaspis maskelli and A. metrosideri are partitioned by their Metrosideros host preferences, with A. maskelli feeding only on lianes or vine species and A. metrosideri only on tree species.
Gall induction by Poliaspis media is prevalent on particular host genera: on Coprosma species it induces rosette shoot galls (Fig. 92); on Hebe species leaf curling; and on Myrsine species leaf roll galls (Henderson & Martin 2006). The galls are formed in plant meristematic tissue (Larew 1990) so that the leaf tip roll on Myrsine australis is induced on an actively growing new leaf, later becoming chlorotic as the scale insects develop and feed on plant cells there (Fig. 93). Although not considered separate distinct species, the populations forming galls may be demes or biological races and may be localised to an area (Henderson & Martin 2006). The new species Symeria phyllocladi is an inquiline in the tubular pocket galls induced by Eriococcus arcanus Hoy, and subsequent feeding by the diaspidid causes chlorosis in those galls compared with the natural green colour of the original eriococcid gall (Fig. 108). Thus, the appearance of the galls can act as a field guide to each of these species (Henderson & Martin 2006).
The most common and widespread of the endemic scales are Fusilaspis phymatodidis (Maskell) (fern scale), Poliaspis floccosa (flax scale), P. media (poliaspis scale), and Symeria pyriformis (pyriform scale). The incidence of flax scale has increased enormously in urban and native restoration areas through the planting of both the natural forms and cultivars of its host Phormium tenax, where the leaf blades can appear ‘painted’ white with their colonies (see Fig. 83). The other three are species of the natural environment, where fern scale is confined to a wide range of ferns. Species of Poliaspis are found in the most far reaching and diverse places of all the endemics, from the Three Kings Islands including the new species P. salicornicola, to the Chatham Islands including another new species P. chathamica, and poliaspis scale is recorded on both Stewart Island and Big South Cape Island. Anoplaspis metrosideri can be found sporadically on leaves of pohutukawa (Metrosideros excelsa) in the North Island, and in much more dense populations on rata trees (M. bullata, M. robusta) in the South Island. No diaspidids are recorded from further north at the Kermadecs (perhaps due to lack of targeted collecting there) or from the subantarctic islands in the deep south.
Most of the adventive, cosmopolitan species are polyphagous and might be expected to invade native habitats, but surprisingly only H. lataniae, H. rapax, and A. nerii do so, yet their impact on native plants is low. Lindingaspis rossi also invades native habitats. It is here considered Australasian, but it may also be considered cosmopolitan as it is polyphagous with 106 hosts listed on ScaleNet (Ben-Dov 2010). Oligophagous adventive species in New Zealand are the two Aulacaspis species (Rubus berry fruits and roses), Furchadaspis zamiae (cycads), and Kuwanaspis pseudoleucaspis (Kuwana) (bamboos). The two Carulaspis species are found only on conifers and Lepidosaphes pallida (Maskell) has been collected only from Japanese cedar in Auckland city. Three of the adventive species listed as occurring here have not been seen since their earlier records and may no longer be present: Lepidosaphes multipora, Parlatoria desolator McKenzie, and Pseudoparlatoria parlatorioides (Comstock). Four adventive species that apparently suffer from New Zealand’s relatively cool-temperate climate, and are found sporadically on indoor or shade house plants, are Abgrallaspis cyanophylli (Signoret) (cacti), Diaspis boisduvalii Signoret (bromeliads more commonly than orchids), Lepidosaphes pinnaeformis (cymbidium orchids), and Pinnaspis aspidistrae (Signoret) (ferns), the latter collected just recently in November 2010 after a gap of 32 years. Apart from Lepidosaphes multipora, the Australasian species are reasonably common and widespread.
Symeria (as Eulepidosaphes) pyriformis is the only endemic non-leucaspidine scale insect species recorded from overseas (on the Isles of Scilly, U.K.) where it was found on a mix of New Zealand native plants and several plants outside its native host range. These were Pittosporum crassifolium, P. bicolour (not N.Z.), P. tenuifolium, Phormium tenax, and Trachycarpus fortunei (not N.Z.) (Williams 1985). It was collected on the bark of the Pittosporum species and this niche may have favoured its successful establishment in the new country if live plants were originally obtained from New Zealand.
Two records of New Zealand species from Fiji are erroneous. The first, Pseudaulacaspis dubia (Maskell) (as Chionaspis dubia and later as Phenacaspis dubia), was mentioned by Williams & Watson (1988) who considered it not the same as P. dubia described from New Zealand. It has now been described as Pseudaulacaspis pyrrosiae Hodgson & Lagowska (2011) (see under Fusilaspis phymatodidis, Remarks, for further details). The second, Poliaspis media, was illustrated by Ferris (1938) based on some specimens from Fiji in the Koebele Collection. This material was examined by me recently and it certainly agrees with Ferris’s illustration, but is equally certainly not conspecific with P. media. Rather, it is close to the Australian species Poliaspis exocarpi Maskell.
Biology and life cycle
Most of the Australasian and endemic species are biparental except that no evidence of males has been found for Anzaspis angusta and Poliaspoides leptocarpi (Brittin). It is possible that A. angusta does have biparental populations in its native homeland of Australia. In the case of the 2nd-instar nymphs of P. leptocarpi, they had variable numbers of ducts (see Fig. 203) and some specimens were sufficiently ductiferous to suggest they might be males. But these ductiferous 2nd-instar nymphs and others with the intermediate and lower ranges of nymphal duct numbers, were all represented in a series of slide-mounted pharate adult female specimens, thus they must all be female. In addition, there was no indication of prepupal, pupal, or adult male stages in any of the collections of P. leptocarpi.
For some other species, males have not been collected but reasonably could exist because the collections were too small to be sure, e.g., Aspidioides corokiae (Maskell), Poliaspis chathamica n. sp., P. salicornicola n. sp., and Symeria leptospermi. Among the adventive cosmopolitan species most are biparental, but A. nerii is uniparental except for occasional biparental populations, whereas H. lataniae and H.rapax are both uniparental.
Male and female diaspidids go through very different post-embryonic development. The female metamorphosis is heterometabolous, they are larviform or neotenic throughout their lives and reach adulthood after two moults. The abdomen of the teneral female is arranged as a concertina that unfolds and expands as she matures to full size. In diaspidines the abdomen then begins to shrink back again during oviposition, leaving space behind the posterior end under the scale cover as a brood chamber for eggs and hatching neonates. Depending on the species and habitat there may be 60–80 eggs in the brood chamber (e.g., Fig. 119) or as few as 6 at a time (e.g., Fig. 50). If the female body size is constrained by a narrow habitat on leaves or twigs, perhaps the oviposition period is more drawn out. After oviposition the brood chamber contains the empty eggshells (e.g., Fig. 68). The eggs of aspidiotines tend to hatch immediately or very soon after they are laid, and the female abdomen does not shrink as much as female diaspidines. Males develop through a holometabolous kind of metamorphosis with non-feeding prepupal and pupal stages to emerge after 4 moults as tiny winged insects (Fig. 85) or, in a few species, as apterous adult males (Fig. 105).
The main dispersal stage is the newly hatched crawler, when males and females are usually indistinguishable. Crawlers may settle close to their natal site, walk some distance for a short time, or be blown to another site if windy conditions prevail (where chance determines if they land on a suitable host plant). A crawler settles by inserting its stylets into the plant and immediately beginning circular motions around the insertion point while spinning its first scale cover (Fig. 90). Time lapse photography has shown that the body regularly rotates alternately from left to right to a maximum arc of more than 360 degrees (Hill & Holmes 2009; http://www.youtube.com/watch?v= 395XmUkWVBg).
The 1st-instar nymphs are now sessile, the females remaining in this position for the rest of their lives and the males until emergence as adults. As feeding continues, waxy material is added to the scale cover, generally in a circular fashion by aspidiotine species and asymetrically towards the posterior forming a more elongate cover in diaspidine species. At the first moult from 1st-instar to 2nd-instar, the nymphs lose their legs and the antennae become unsegmented tubercles with 1 or more setae. Stylets are not withdrawn from the plant tissue and new larger stylets are formed that may follow the same direction within the plant as the 1st stage stylets or change direction. Sometimes stylet tracks can be visible if the damaged plant cells change colour, as in the 2 sizes of red stylet tracks of Anoplaspis metrosideri on Metrosideros leaves (Fig. 17) and brown stylet tracks of Lindingaspis rossi (Fig. 69–70). Sexual dimorphism is now apparent in the 2nd-instar nymphs with the male cover usually smaller and more elongate in shape than the female cover.
Number of generations per year. Adventive species may have 1–3 generations per year (Timlin 1964b; Charles & Henderson 2002; Miller & Davidson 2005). Endemic species are probably mostly univoltine (one generation per year) but are not synchronised to a particular season, so that generations at a location overlap in time, particularly for females that produce their eggs a few at a time. In New Zealand, the influence of evergreen forest with year-round available food source and temperate climate reduces the need to complete reproduction in narrow seasonal time frames, compared with the habitat constraints of deciduous forests and/or colder climates.
In New Zealand, many of the adult females and their eggs are bright yellow (e.g., Anzaspis spp., A. nerii, Hemiberlesia spp.); pale (e.g., Diaspis boisduvalii, Furchadaspis zamiae, Lepidosaphes spp., Symeria pyriformis); purple-black (Anoplaspis metrosideri); pink (A. maskell); pink-red to chestnut (e.g., Aulacaspis rosarum Borchsenius, Carulaspis spp.,) or purplish (L. rossi, Parlatoria spp., Poliaspoides leptocarpi). The female body colour may be a useful diagnostic tool for scales with similar covers, e.g., San José scale (dark cover, yellow body, see Fig. 43,) and Ross’s black scale (dark cover, red-purple body, see Fig. 68).
The scale cover (see Fig. 1, 2) in diaspidids differs significantly from the waxy coverings of those of other coccoid families in that each cast nymphal skin is retained and incorporated in the cover, along with waxy exudates from the insect’s glands (Foldi 1990; Ben-Dov 1990). All 2nd-instar nymphs have the 1st-instar skin or exuvium as part of their cover. At the next moult the male loses his mouthparts and ceases feeding, so remains under the same cover of the 2nd-stage while proceeding through a prepupal and a pupal stage to reach adulthood (Fig. 24–25), the later nymphal skins being shed beneath the cover. In contrast, the female becomes adult at the second moult and continues feeding, while the 2nd-instar nymphal cast skin is retained and incorporated in her cover underneath and slightly behind the 1st-exuvium (Fig. 26–28). The female continues to add a great deal more waxy area to her cover as her body expands to maximum size at maturity, and when that is achieved, an extra crawler flap is added to the posterior end to allow emergence of neonate crawlers.
Aspidiotine scale covers are generally of a round shape with central, subcentral, or lateral exuvia, whereas diaspidine scale covers are generally more elongate and the exuvia are terminal. An exception mentioned here is the Leucaspidini, that are purportedly aspidiotine in the phylogenetic analysis of Andersen et al. (2010, Fig. 1, Clade E) but possess diaspidine-shaped elongate scale covers and terminal exuvia.
In pupillarial species the 2nd-instar nymphal skin becomes sclerotised (to various degrees in different species — for example, it is pitch black in Trullifiorinia acaciae) and at the moult it detaches from, and completely encloses, the membranous 3rd-instar (adult) female. The 1st-exuvium and wax cover remain. The preferred term for this 2nd-instar nymphal skin is the pupillarium (Henderson et al. 2010). As the adult female matures, a slit forms at the posterior end of the pupillarium to allow crawlers to exit.
In aspidiotines the 1st-nymphal skin is shed by rupture around the margin of the body. Features such as the antennae on the ventral portion become part of the ventral scale where they may be overlooked or lost on the substrate, and the dorsal portion above the insect’s body is substantially without taxonomic features (MacGillivray 1921). In diaspidines the 1st-exuvium splits at the cephalothorax, with the mouthparts, spiracles, legs, and other parts of the venter bundled together towards the posterior end, leaving the body margins including head, antennae, and pygidium plus all of the dorsum intact. This feature can provide valuable taxonomic information (e.g., Fig. 180, 188, 199, and see species distinctions under Anzaspis). The 2nd-exuvia of both aspidiotine and diaspidine taxa are moderately informative and generally indicate a simplified morphology of the adult female to which they are attached (Fig. 201).