Most of the information below is based on Williams and Watson, 1988. Structures mentioned below are explained and illustrated more fully in the glossary, which can be accessed by clicking on words in blue.

Scale cover
In all the species of Diaspididae covered in this work, a fibrous scale cover is produced, incorporating the exuviae of the previous stage(s). The first instar is mobile and locates a feeding site before settling to feed and begin secreting a waxy cover. The second instar incorporates the exuviae and waxy cover of the first instar into its own scale cover, and adds material to the outer edge to increase its diameter, covering the growing insect.

In the female, the adult adds material to the edge and underside of the exuviae and scale cover of the second instar.The material added to the scale consists of fibrous secretions from [l][m]Glossary[/m][r]abdomen[/r]abdominal ducts, glued together with faecal material from the anus and moulded by movements of the pygidium and the lobes thereon. In life, adult females are recognisable by the presence of two exuviae in the scale cover SCALES.jpg unless the species is pupillarial, in which case there is only one exuviae present in the adult scale cover PUPILLAR.jpg. The scale cover may be circular or more or less elongate oval, with the exuviae located either centrally, sub-centrally or marginally. The shape of the cover approximately indicates whether the body of the adult beneath it is circular or elongate.

In the male, the scale cover is not enlarged after the second instar stage, so it only contains the first instar exuviae. The scale cover of the immature male can be recognized in the field by the presence of only one exuviae and by the shape of the scale, which is smaller and usually more elongate than that of the female.

The general shape of the scale cover is often characteristic to the genus. Colour and details of the shape may vary according to species, host-plant, environmental conditions and stage of development. This makes identification in the field rather unreliable unless you are very familiar with the local fauna. During preparation of Diaspididae for identification, the cover is removed but it is useful to keep a note of its appearance in life, as this may assist identification.

In pupillarial species, the morphology of the second instar exuviae is taxonomically useful and examples should be mounted on slides together with the adult females.

Body of the adult male
ASPNEMAL.jpg
Diaspidid scale insects show pronounced sexual dimorphism. Adult male Coccoidea are small, fragile and usually possess a single pair of delicate wings. The hindwings have been reduced to a single pair of halteres, each bearing a hook-like hamulus (collectively called a hamulohaltere). Wingless, or even degenerate larviform males occur in some species. All adult male Diaspididae possess obvious external genitalia and lack functional mouthparts or a 'neck' . They are short-lived, due to their inability to feed, and are seldom collected. CHFURM.jpg

In the ancient scale insect family Margarodidae, males of most species pass through a single pupal stage before emerging as adults. However, in some Margarodidae and in all other families of Coccoidea including the Diaspididae (so far as is known), males pass through two non-feeding pupal stages (pre-pupa and pupa). These stages use stored food accumulated during the first and second instars. There is no reliable means available to identify diaspidid males to genus or species. At present, the identification of species of Diaspididae is entirely based upon the morphology of the sessile adult female.

Body of the adult female
The sessile adult female diaspidid is more or less larviform, with antennae reduced to stubs, and legs absent or very reduced. Her head is closely fused with the anterior two or all three thoracic segments, almost without any indication of the segmentation. On the abdomen, the separation between segments is fairly distinct and can be interpreted by following the segmental marginal setae (one pair each of dorsal and ventral setae on each segment), the marginal constrictions and the intersegmental lines. There are 8 or 9 abdominal segments (Ben-Dov, 1990a) CHRYSOGD.jpg; the posterior 5 segments of the abdomen are more or less fused together and sclerotized to form a pygidium. The adult female is distinguishable from the second instar in possessing a vulva, and sometimes disc pores, on the ventral surface of the pygidium.

Identification of most species is based on the morphology of the adult female, especially using the structures associated with formation of the scale cover. These include the type, size number and distribution of ducts; and the form, sclerotization and arrangement of lobes and plates/ gland spines along the margin of the body, especially on the pygidium. The presence/ absence, number and arrangement of: disc pores, duct tubercles, lateral tubercles, eyespots modified into spurs, and dorsal bosses are additional useful characters.

In pupillarial species, where the adult female remains inside the cast cuticle of the second instar PUPILLAR.jpg, the structure of the adult female is often simplified and her cuticle very membranous. In these species, details of the second instar pygidium are sometimes used to assist identification. Pupillarial species require extra care in preparation for identification (see Methods module, Make slides field).