POLYPHAGA Emery, 1886
TENEBRIONOIDEA Latreille, 1806
3
3
1.5-2.5mm
ADERIDAE Csiki, 1909
Ant Leaf Beetles
Only one of our three species (Aderus populneus) is likely to be found, at night or swept from flowers, while the other two are very local and rare.
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Around the World
This is a cosmopolitan family of about 1200 species in 50 or so genera. The majority occur in tropical regions and northern temperate regions are relatively poor in diversity; 11 genera occur in the U.S.A and 10 in Europe. The Australian fauna includes 11 genera. More than half of all described species are included in the genus Aderus Stephens, 1829 but this is unlikely to remain the case e.g. the majority of Australian species are included but it is doubtful whether they will remain or even that they should have been included in the first place.
Ecology
Most species are saproxylic and the adults may be sampled by beating the foliage of host trees during warm weather, Berlese extractions of wood debris from hollow trees etc., rearing adults from wood samples, searching under bark, using malaise or other flight interception traps, from blossom in the spring or at light as they fly nocturnally. The larvae grow up to 6mm and are cylindrical or weakly flattened and lightly sclerotized, usually pale cream or white in colour and sparsely covered with setae. They have robust well sclerotized and asymmetric mandibles, well developed legs and strongly upwardly curved urogomphi. Most occur in decaying wood, leaf litter or the nests of other insects. Some aderids are specialists e.g. some Aderus and Euglenes Westwood, 1830 live in the Batu caves in Malaya while at least 3 species of Megaxenus Lawrence, 1990 develop in termite nests in Australia and New Guinea. There seems to be no modern consensus on the classification and it appears to be one of the least understood groups within the Tenebrionoidea.
Description
With the exception of the genus Megaxenus where the adults are up to 7mm all members of the family are small <4mm. In general appearance they resemble anthicids, ptinids or even small cerambycids but with experience they are quite distinctive. In outline they are elongate-oval, although some species of the widespread tropical genus Mixaderus Collado & Alonso-Zarazaga, 1996 have almost round elytra, with a relatively broad head and a constricted neck, a quadrate pronotum which narrows anteriorly and elongate, often almost parallel-sided elytra, with
prominent shoulders. They are mostly drab coloured brown or grey and some have various patterns to the elytra; generally pale or dark transverse fascia on a contrasting background. The dorsal surface is often finely pubescent. In most the head is strongly inclined anteriorly with large protruding eyes that variously encircle the antennal insertions and temples that are constricted behind the eyes. The labrum is well-sclerotized and visible from in front, and the palpi are often well-developed with the terminal segment of both usually expanded and truncate, subtriangular or securiform. Mandibles bilobed or bidentate at the apex and often with a tooth on the inner margin. Antennae 11-segmented and pubescent; usually filiform or weakly serrate although in some tropical species distinctly serrate and in some Nearctic species of Emelinus Casey, 1895 e.g. E. melsheimeri (LeConte, 1885) strongly pectinate. In many species they are dimorphic, varying in length and the proportions of the segments e.g. in some species of Euglenes the distal segments in the male are very much more elongate than those in the female. In many species the segments are transverse, sometimes widely so, and the antennae are gradually thickened or appear to be weakly clubbed. The antennal insertions are sometimes visible from above. Pronotum quadrate or nearly so and usually narrowed anteriorly, without lateral borders and narrower than the elytral base. Sometimes the lateral margin is angled and narrowed to the front and hind margins. Scutellum conspicuous; flat and truncate to emarginate. Elytra entirely covering the abdomen and usually randomly finely to very strongly punctured, in some species there are distinct striae although a scutellary stria is never present. Wings usually well developed and most species fly well. Abdomen with 5 visible sternites; 1 & 2 fused, 4 & 5 variously fused or articulated. Legs long and slender with very small tibial spurs. Tarsi 5-5-4 with segments at most only weakly lobed; basal segment long, penultimate segment small and usually hidden by the lobes of the antepenultimate segment. Claws simple.
UK Species
Species Key
1.
Antennomeres 2 and 3 strongly rounded and distinctly shorter than the fourth.
Third antennomere at least as long as the fourth
2.
Head and pronotum black, elytra brown. Eyes widely curved around the antennal insertions. Antennae sexually dimorphic; in the male segments 3-11 elongate, in the female 9 and 10 are quadrate or nearly so.
Unicoloured dark to pale brown. Eyes much less strongly curved around the antennal insertions. Antennae short; segments 6-8 transverse in both sexes.