Microcoryphia

Synonyms: Archeognatha, Ectotrophi (in part), Ectognatha (in part)

Common name: bristletails

Small or moderately sized apterygote insects; head with long multiannulate antennae, large contiguous compound eyes, ocelli, ectognathous chewing mouthparts, mandibles with single articulation, maxillary palps 7-segmented; thorax strongly arched with terga extending over pleura, legs with 3 (rarely 2) tarsal segments; abdomen 11-segmented, though 10th segment reduced and tergum of 11th forming median caudal filament, paired styli present on each abdominal segment, long cerci with multiple subdivisions present.

As noted in the Introduction to this chapter, Microcoryphia and Zygentoma (see Section 6) were originally united in the order Thysanura. However, fundamental differences in their structure (compare the definitions of the orders) have led to their separation as distinct orders. The Microcoryphia form a small (about 350 species) but cosmopolitan group, with about 35 species in North America (mostly Machilidae), 7 in Australia (all Meinertellidae), and 7 in Britain (all Machilidae).

Microcoryphia (Figure 5.4A) are elongate insects up to 20 mm in length. Their body is strongly convex dorsally (with the large terga extending around the sides to cover the pleura), generally tapered posteriorly, and covered with scales. The head is hypognathous, in some species prognathous, and carries prominent chewing mouthparts, the long, 7-segmented maxillary palps being particularly conspicuous. Each mandible has a single articulation with the head. The antennae are filiform and comprise 30 or more subdivisions that lack intrinsic musculature. Compound eyes are well developed and contiguous (meet in a middorsal position). Median and paired lateral ocelli are also present. The legs have three tarsal segments and, in some species, those of the mesothorax and metathorax bear coxal styli. Abdominal styli occur on segments 2-9, and eversible vesicles are almost always found on abdominal segments 1-7. In females an ovipositor is formed from the appendages of

Structure

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