Description

Brentids vary greatly in size and general appearance but from the European perspective the Apioninae and Nanophyinae are quite distinctive and unlikely to be confused with other groups. More generally they vary from about 1mm, in the smallest apions, to about 100mm in some Brentinae. They are usually very elongate and parallel-sided with a long rostrum and appendages, glabrous or nearly so and drab brown in colour, sometimes with pale yellow, orange or red markings. With the exception of the Nanophyinae the antennae lack a distinct scape, the remainder may be simply filiform with all the segments quadrate to very elongate, or short and clubbed where the club may be elongate and loose, compact or, in Cycladus, with fused segments. The head is usually elongate, often with long cheeks and temples and usually with small and very convex eyes, the vertex etc. is often heavily sculptured and the mouthparts at least partly atrophied with the labium and maxillae reduced, rigid and reduced maxillary and labial palpi which are partly or wholly hidden on the labium and fused gular sutures. The pronotum is usually elongate and without lateral borders; the shape varies widely; it is usually curved laterally and may broadest anterior or posterior to the middle, the angles are usually distinct and the surface variously sculptured but often with deep longitudinal sulci. The elytra are elongate and flattened, usually with distinct and often strongly punctured striae, and sometimes with the suture raised or with various longitudinal depressions, the declivity may be simple or lead to a produced and flattened apical area, and they are usually continuously rounded and completely covering the abdomen. Most species are fully winged and fly well. The first two abdominal ventrites are fused and usually much longer than the others; often longer than the remainder combined. The legs are very robust and often long; with variously thickened, clavate or otherwise developed femora, tibiae which may bear strong teeth or other sculpture and 5-segmented tarsi, usually with the third segment lobed. Many species display obvious sexual dimorphism with the males having much more developed rostrum and mandibles and sometimes more developed appendages. There is no doubt that this is an awkward group in terms of classification and definition as there are so many features and combinations of features in common with the true weevils, and in any case they just look like weevils in the broader sense, but even if the monophyly of the family is only weakly supported-there are only two synapomorphies, one larval, the other  the reduction of the number of Malphigian tubules to four-it is becoming increasingly evident that this is a sister group of the Curculionidae in the widest sense.

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Ecology

The majority of brentids inhabit wooded tropical areas and diversity can be high in the rain forests of tropical Australasia, most are wood borers and occur under bark, they are both diurnal and nocturnal, feeding as adults on fungi, sap and other insects. Some are myrmecophilous, living in the nests and galleries of various ants. Larvae bore through the wood of dead and damaged standing or fallen timber, feeding upon various fungi and yeast; and some species are known to oviposit in the galleries of Scolytinae and Platypodinae, ejecting or killing the host larva in the process. This saproxylic lifestyle is distinct from our familiar Nanophyinae and Apioninae although species of Cylas Latreille, 1802 are stem miners of various herbaceous plants; C. formicarius Fabricius, 1798, which is a pest of sweet potatoes and now occurs in warmer regions throughout the world, oviposits in stems near the ground or even among stored potatoes and the larvae develop and pupate in the fruits.