What Bug Is That? The guide to Australian insect families.

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Cecidomyiidae

Overview

The family Cecidomyiidae comprises small, fragile flies to which the vernacular name of 'gall midges' often is applied. This reflects the frequent, but by no means universal, larval habit of gall-inducing in plant tissues.

The Cecidomyiidae are a species-rich family, with over 3,000 species described. In Australia the diverse and rich fauna is not reflected in the number of described species. Only certain pest species have been well studied. Perhaps no more than 25% of the described species (numbering some 250 species) are allocated correctly to a modern generic concept.

The fauna includes several species introduced as biocontrol agents. There is an erroneous Australian record of the pestiferous Mayetiola destructor - the presence of this species has not been confirmed yet.

Among immature stages of Cecidomyiidae are many larvae that induce plant galls (especially in subfamily Cecidomyiinae), and others that are feed on plant parts, including flowers, without inducing galls. Gall shapes and hosts are characteristic and often species-specific. In the subfamily Lestremiinae, many larvae are mycophagous, including some that live in commercially cultivated mushrooms. Certain larval Cecidomyiinae are predatory on mites or coccoids, and some are aphid, psyllid and coccoid parasitoids. Mycophagy and xylophagy are quite frequently encountered.

The pupa may develop in the larval habitat or the late stage larvae may crawl to another site to pupate. Some species are paedogenetic.
This family contains wingless species.

Description

Adult Cecidomyiidae are recognised by their elongate antenna and distinctive wing venation, with few weak veins. The costa is continuous round the wing, although sometimes interrupted just beyond the apex of R5. Amongst the few other families with such a costa, the tarsomere structure usually is distinctive:  tarsomere 1 is much shorter than 2, and both tarsomeres are more or less fused. Thus each tarsus appears to be, at most, 4-segmented. Lestremiinae, which are small fragile midges with weakly veined wings, differ in having ocelli often present. This family contains wingless species.

Cecidomyiid larvae are apodous and atypical nematocerans in that the head capsule is very small, with all appendages very reduced in size, and often there is a distinctive spatulate structure in the prothorax.

Distribution

Cecidomyiidae are cosmopolitan and globally distributed, with the exception of Antarctica. The Australian cecidomyiid fauna appears to contains widely distributed genera, with some (perhaps underestimated) endemism and some radiations associated with certain of Australia's endemic plant radiations.

  • Cecidomydidae

  • Cecidomyiidae, small primitive fly

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