Description

Although most ‘weevils’ are readily recognized, species of Dryophthoridae, Erirhinidae and Raymondionymidae will conform to any general description because there is so much morphological overlap, but these families differ fundamentally in that the aedeagus is divided by a distinct lateral line into upper (tectum) and lower (pedon) parts, this pedotectal form is never seen in the ‘true’ weevils of the present family, and this difference is the basis for promoting the 3 former subfamilies to full families. Various other beetles also have a distinct rostrum e.g. some salpingids and mycterids (Tenebrionoidea), but they are always distinct in other ways.  Adult weevils vary from about 1mm to 40mm although the majority are between 2 and 20mm, the shape is very variable but generally elongate to very broadly oval, either continuous or discontinuous in outline and from strongly flattened to very convex, usually with the head, pronotum and elytra separately so. Colour varies very widely but the majority are rather drab, from black to testaceous, many are brightly coloured, sometimes brilliantly so, especially in tropical regions, and many are covered with recumbent or appressed scales which are often brightly coloured and metallic and form patterns, and fine pubescence, many are glabrous, or nearly so, or have erect or sub-erect setae. The form of the dorsal sculpture varies enormously but most are smoothly convex and lack major sculpture, especially those in temperate regions, but many exceptions occur, especially in the tropics where some truly striking examples of structural modification occur. The head is often proportionally small, generally prognathous and variously inserted into the prothorax so that some or all of the temples are concealed (many exceptions occur), with the eyes on the lateral margin or occupying much of the lateral and dorsal area. The eyes vary in size, shape and convexity and in some are reduced or absent. The rostrum varies from very short and broad, sometimes indistinct, to very long and narrow, in many it is curved downwards and sexually dimorphic; longer, narrower and with the antennae placed nearer the base in the female. In most cases there are lateral or dorso-lateral scrobes into which the antennae fold and which protects them when the weevil is boring into host material. Antennae often long and slender, usually geniculate with a 5-7 segmented funiculus and a distinct 1-3 segmented club. Mouthparts mounted at the rostral apex; mandibles short and broad, in some with a deciduous process or scar at the apex, labial palps 1 or 2 segmented, rarely absent but in some recessed into cavities on the ventral surface of the prementum, maxillae sometimes concealed by an apically expanded mentum, in some with distinct galea and lacinia. Pronotum extremely variable; widely transverse to very elongate although in most near-quadrate, and, in warmer regions, with a wide range of sculpture. Elytra equally variable, from flat to evenly convex, smooth or sculptured and shiny to heavily microsculptured or striate, in many scolytids the elytra are adapted to wood-boring, the apex is excavate and toothed along the lateral margin, modifications that help push against the side of the galleries and clear away wood dust and frass. In some terrestrial forms the elytra are fused. Ventral surface of the thorax very variable, coxae contiguous to widely separated, sometimes with grooves for the antennae and legs. Abdomen generally with the two basal ventrites connate, only very rarely free, tergites 7 and 8 form a pygidium which is generally hidden beneath the elytra although any exposed segments tend to be heavily sclerotized or sulcate. Legs extremely variable, often long and robust with the femora clavate and the tibiae toothed internally and/or apically. Some species of Rhamphini have greatly enlarged hind femora which allow them to jump in much the same way as the alticine Chrysomelidae. Tarsi generally 5-5-5 with the third segment bilobed and the fourth diminutive, the terminal tarsomere is often elongate. In most with paired claws, sometimes connate and undeveloped, often free and lobed basally, sometimes serrate etc. Scolytinae and Platypodinae differ from the rest; they are small beetles, 1-9mm but mostly between 1 and 4mm, cylindrical or weakly flattened dorsally and most are heavily sclerotized, the majority are drab black or brown and pubescent, in some with distinct scales. Distinguished from other groups by the presence of pre-gular sutures; a distinct pre-gular sclerite between the median gular suture and labial articulation, the rostrum is short or absent and the tibiae, or at least the pro-tibiae, possess teeth or recessed stout setae along the outer margin.