BRENTIDAE Billberg, 1820

Straight-Snouted Weevils

Sometimes classed as two separate families, these small weevils are generally abundant in a wide range of habitats.

Suborder:

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POLYPHAGA Emery, 1886

CURCULIONOIDEA Latreille, 1802

2

36

89

0.7-4.5mm

Around the World

This cosmopolitan group of Orthocerus weevils includes about 4000 species in 400 genera, numerous tribes and at least 4 subfamilies although several tribes are often given subfamily status; the classification has been the result of much recent revision and as a result the group now includes 3 groups formerly included within the Curculionidae; Apioninae Schoenherr, 1823, Nanophyinae Gistel, 1848, and Cycladini Schoenherr, 1823. In general the family is by far most diverse in old world tropical regions, and more especially Australasia, but both Apioninae, which includes about half the species, and Nanophyinae, with about 300 species, are very diverse in temperate areas.  Ithycerinae Schoenherr, 1823 includes a single monotypic genus; Ithycerus noveboracensis Forster, 1771, commonly known as the New York Weevil, is a saproxylic species widespread in North America, it superficially resembles an entiminid weevil and was formerly included in the Curculionidae. After Apioninae the Brentinae is the largest subfamily with the majority of described species in almost 200 genera and 6 tribes although several systems will be found in the literature where various tribes are given subfamily status. Africa and Australasia are the most diverse regions but most warmer areas have diverse faunas including central and tropical South America. The following tribes are represented in the Palaearctic region, Cyphagogini Kolbe, 1892 includes more than 400 species in 70 genera and is mostly African and Australasian in distribution with only a few New World species; 64 species of 15 genera and 3 subtribes occur in the Palaearctic region although the majority are from eastern Asia and oriental regions and none occur in Europe. The Cycladini or ‘sweet-potato weevils’ is a monogeneric group native to warmer regions of the Old World but now widespread in the New World following introductions; 2 species occur in Asia.  Thrachelizini Lacordaire, 1865 includes 23 genera and is most diverse in Southeast Asia and Australasia with very few New World species; the Palaearctic fauna includes 21 species of 11 genera and 3 subtribes and is entirely eastern and Oriental with none occurring in Europe. Brentini Billberg, 1820 includes about 90 genera and is well represented in all the warmer regions; 52 species of 7 genera are Palaearctic but more or less restricted to eastern and south-eastern Asia and the Oriental regions, and only a single species, Orfilaia reichei Fairmaire, 1859, is recorded from Europe (Greece). Despite the group being absent from most of Europe there is a diverse fauna across North Africa.

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.

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.

UK Subfamilies
  • NANOPHYINAE:

    • Antennae geniculate; funiculus 4-6 segmented, 5-segmented in Palaearctic species, scape >half the length of the remainder of the antenna. Pronotum campanulate; the base as broad as the base of the elytra, and strongly narrowed to the anterior margin. Body continuous in outline. Basal abdominal sutures recurved laterally.

  • APIONINAE:

    • Antennae orthocerous; funiculus 7-segmented, scape at most less than half the length of the remainder of the antenna. Pronotum parallel-sided, rounded or weakly narrowed anteriorly, the base narrower than the elytral base so that the outline is discontinuous. Basal abdominal sutures straight.

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