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

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Simuliidae

Overview

Simuliidae, comprising some 1500 species worldwide, are one of the most medically significant groups of Diptera. These characteristically hump-backed, small flies include many voracious vertebrate blood-feeders, such as those that transmit parasites including onchocerciasis (river blindness). Fortunately, in Australia there is little evidence of vectorial status amongst the few species known as human biters, but simuliids may transmit cattle onchocerciasis and act as mechanical vectors of myxomatosis in rabbits. Amongst the few serious pests of humans, Austrosimulium pestilens undergoes periodic mass outbreaks in central Queensland, following flooding of seasonal rivers.

There are a number of taxonomic problems amongst the Australian Simuliidae. The first concerns precise species delimitation. Elsewhere in the world, many morphologically defined taxa have been found to be composites of 'cytospecies', differing chromosomally (and often vectorially) but inseparable on morphology. Limited evidence suggests that this situation is also true in Australia, but the consequences for species identification and nomenclature have not been published. Secondly, the name Cnephia Enderlein has been used for Australian Prosimuliini, although it has long been recognised that the name should be applied only to an Holarctic genus. The necessary studies to establish the true status and relationships of Australian ' Cnephia ' have not been made, but a recently described Western Australian species in this group has been referred to Paracnephia (Moulton et al. 2004); it is implicit that other ' Cnephia ' also can be placed under this named taxon.

The larvae filter-feed on debris and diatoms which are strained from the water column using the cephalic fans. Number of larval instars is relatively - high up to nine. Pupation  occurs in the larval site - a pad of silk is spun, then a cocoon of silk in which the pupa develops.

Description

Adult blackflies are typically hump-backed, with antennae short, about as long as head; and with the flagellum shortly setulose in both sexes. The wing is broad, with weak posterior veins.

Larval Simuliidae are amongst the most characteristic of running-water macroinvertebrates. In life, the body shape, and posterior anchorage on rocks and dangling vegetation in flowing water are characteristic. When preserved, and the anchorage is lost, but they are recognisable by the cephalic fans on the head (which collapse on dying but are still distinctive) and the circlet of spinules around the posterior end, which acts as a sucker in life.

Distribution

Simuliidae are cosmopolitan and distributed globally, with the exception of Antarctica. The Australian simuliid fauna of 36 species appears to contain Southern Hemisphere endemics ( Australosimulium ) and some radiations of Paracnephia -like species that evidently also have austral (Gondwanan) affinities.

  • Simuliidae larvae

  • Simulidae larval instar stages

  • Aquatic larvae of Simuliidae in a rocky creek bed

  • Simuliidae

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