FNZ 51 - Coccidae males (Insecta: Hemiptera: Coccoidea) - Introduction
Hodgson, CJ; Henderson, RC 2004. Coccidae (Insecta: Hemiptera: Coccoidea): adult males, pupae and prepupae of indigenous species. Fauna of New Zealand 51, 228 pages.
(
ISSN 0111-5383 (print),
;
no.
51.
ISBN 0-478-09360-8 (print),
).
Published 22 Jun 2004
ZooBank: http://zoobank.org/References/85A2C19D-CA28-4C43-9B7C-BABE3D5DFCE8
Introduction
This paper describes the prepupae, pupae, and adult males of indigenous New Zealand soft scales, as far as the available material allows. Thus 43 species of indigenous soft scales are currently known from New Zealand and, of these, 21 prepupae, 27 pupae, and 31 adult males are described below. Introduced species are not covered.
This is only the second study on adult males of any scale insect group for a complete geographic area and the first to include the pupae and prepupae. The likely importance of the structure of the latter two groups in helping to understand the relationships within the family Coccidae is not yet known but knowledge of the structure of the adult males is considered to be essential.
Most studies on scale insects to date have been on the long-lived, and reasonably easily collected, adult females, although recently there has been a move to include the descriptions of other stages and these are proving useful in helping to confirm identifications and in clarifying taxonomic relationships. However, studies of the short-lived and rarely collected adult males have begun to offer real support to classifications based on phylogenetic analyses. This is because, although the adult females have relatively few characters and have a more "plastic" structure (which might allow them to undergo convergent evolution more easily than the more uniform males), the homology of adult male characters is much less doubtful, even between coccoid families, and there is an abundance of characters. Therefore this paper should provide a strong basis for a later phylogenetic study of the New Zealand soft scales, which is planned once all the immature stages have been described.
The history of scale insect taxonomy in New Zealand was described in the earlier volume (Hodgson & Henderson 2000), along with comments on the scale insect classification, biology, life cycle, distribution, host-plant associations, economic importance, predators and parasites, and collecting and mounting methods. Nevertheless, some of these topics need to be slightly augmented for this volume on the prepupal, pupal, and adult male stages.
Biology and life cycle. The life stages of a soft scale are shown in Fig. 1. The crawlers of male and female soft scales appear to be morphologically identical and it is this stage that does most of the dispersal. After a short feeding period and some growth, the crawler moults to become a 2nd-instar nymph and here the male and female nymphs can be fairly easily separated. Although both female and male 2nd-instar nymphs have well developed mouthparts and can feed, and both secrete a glassy wax tent or test which completely covers the body, the shape and structure of these tests are sexually dimorphic.
The male test functions more like a box or garage (Henderson & Rhode 2001) and is firmly attached to the host-plant along its margin by wax secreted by marginal tubular ducts. This test forms a protective cover within which the insect undergoes metamorphosis, protecting it against environmental stress such as dehydration, etc. Eventually the 2nd-instar nymph moults into the 3rd stage referred to as the prepupa. The prepupa lives beneath the test secreted by the 2nd instar and does not feed. Eventually it moults into another non-feeding stage called a pupa and then finally into the adult male, still beneath the glassy test of the 2nd instar. This male cycle takes as long as that of the female so that the males emerge at the same time as the adult females.
The test of female indigenous coccids is constructed of a series of wax plates that increase in size as the insect grows and that are separated by sutures. In the tests of all known indigenous male coccids (Fig. 3-12), except the two Pounamococcus species, the wax plates are all fused together to form a rigid cover, but with an additional single suture separating a hinged plate at the posterior end (the back plate of Henderson & Rhode 2001) that eventually allows the male egress from the test after eclosion. Oddly, this back plate suture forms across the median of a transverse row of fused plates, rather than along an original suture line between plates (Fig. 7-11). However, the male tests of the two Pounamococcus species are constructed differently, with the plates not fused together (Fig. 13) but rather held together by criss-crossed wax strands on the inner surface of the sutures (Fig. 14). These joining wax strands are lacking on the lateral and median sutures near the posterior end of the test, thus forming an equivalent back plate, although the strands do form a pair of hinges on the corners where these plates meet.
During metamorphosis, the sticky wax holding the margin of the back plate to the substrate weakens, enabling the back plate to be lifted up a little. At each successive moult, the exuvia is shucked off posteriorly as the male wriggles to the posterior end of its test. At the same time, the back plate flexes upwards while held in place by a pair of wax hinges (Fig. 12), very much like a tilting garage door, and the exuvia is pushed out from beneath it (Fig. 2). The insect then moves forward inside the test and the back plate closes down again, apparently under its own weight. After the final moult to adult, the male rests inside the test for 2-3 days while its wings harden and its caudal wax filaments (if it has them) are produced. The white wax filaments protrude from under the back plate when fully developed; their function is unknown. The adult male emerges backwards with its wings folded across its body, possibly forming a smooth surface to slide beneath the test and protect the more delicate abdomen. The antennae are held along the body length until after emergence when they are spread to the side and forwards and may be used as tactile appendages.
Being particularly fragile and short-lived, adult male coccids are seldom collected live in the field unless still in their pre-emergent phase, when they can be brought into the laboratory and observed. The emergence of an adult male from its test has not been fully observed, because they tend to come out after dark. However, the mechanics of emergence can be demonstrated by the structure of the test and the way it functions during the expelling of prepupal and pupal exuviae by the late-stage males (Henderson & Rhode 2001; Fig. 2). When collected on leaves or stems cut from the host plant, we have had some success rearing adult males from the pupal stage, but usually not from prepupal stage and never from the 2nd-instar.
The stance of an emerged adult male tends to be with head held higher than the rest of its body, appearing to "look around" rather like a jumping spider, and with its forelegs straighter than the other 2 pairs of legs. Flight take-off is very quick and may in part involve a spring into the air. Prior to flight, the wings are held in a delta shape, not meeting along the mid-line. The caudal-wax filaments may drag on the substrate or be flicked up when the abdomen is flexed upwards. The dorsal eyes appear to be used for orientating with the light and the ventral eyes for searching the substrate. Full mating has not been observed, but adult males, presumably attracted by chemical stimuli in particles of remaining waxes, persisted in the exploration of sites from which females had been removed. The males then bent the abdomen down and forward as though trying to insert their penial sheath into the site.
The bodies of most live adult males are usually variations of brown, sometimes more red-brown or lighter pinkish-brown, with dark eyes that may be dark brown or black. However, the adult male of Inglisia patella is pale yellow with red eyes, and the male of Aphenochiton pubens is pale green on the abdomen and light brown on the thorax. The head, thorax, and legs of all males appear much darker than the abdomen because they are more sclerotised. The wings are usually pale beige, with the radial vein forming a slightly darker line.
The structure of the male test can be very useful in identification. As their name suggests, Plumichiton species often have ornate wax plumes, that of Plumichiton elaeocarpi being particularly fine, with glassy-wax curls around the edge and softer plumes curling forwards like waves in the middle. The male test of Lecanochiton scutellaris also has a soft wax plume that resembles a tiny sail. Of the species that have rows of glassy wax plates in their tests, interspecific differences are less obvious, e.g., the tests of Ctenochiton species cannot be differentiated, nor some Aphenochiton species, but most tests of species in other genera, e.g., Crystallotesta , Inglisia , Epelidochiton , Kalasiris, and Pounamococcus , are fairly distinctive. Where the test is relatively transparent, the colour of the male inside may aid identification.
Host-plant associations . As indicated in Fauna N.Z. 41 , although the males tests are found usually on the same plants as the female stages, the plant host range of male soft scales seems to be slightly wider than for the females, with the male stages occasionally being found on other plants. This can lead to problems of identification although, if there is only one soft scale species in the immediate vicinity, it is likely that the male stages belong to it.
Identification of adult males in W.M. Maskell's collection. Males of some soft scale species were collected by Maskell and these are mentioned in the text. However, it can be very difficult to be sure as to which species any male collected in the wild actually belongs once it has left its test. In most instances, the material used in this review was bred out from pupae or from tests that contained adult males at the time of collection. These were usually fairly closely associated with other known stages (usually the adult female); their identity was therefore known with some confidence. The conditions under which Maskell collected his males are unknown, and it is here considered that some of these are unlikely to be the species he believed. A good example of this is the male of Aphenochiton inconspicuus (Maskell), which is clearly not conspecific with the material since collected under the conditions outlined above.
Further taxonomy . The original generic revision of the New Zealand soft scales was based only on adult female characters. Now that the prepupae, pupae, and adult males of about half of these species have been studied, it is clear that some changes may need to be made to the pre-existing arrangement. Thus, within Aphenochiton, A. inconspicuus (Maskell) (the type species) does not appear to be congeneric with the other species currently in this genus. Similarly, in Crystallotesta (type species C. fagi (Maskell)), C. ornata (Maskell) and C. ornatella Henderson & Hodgson are not congeneric and probably merit a new genus. Further research is being undertaken to determine whether creation of new genera for these species is appropriate.