CRYPTOCEPHALINAE Gyllenhal, 1813
Includes a variety of species found on herbaceous and woody vegetation. The majority are very local and rare.
This is a cosmopolitan subfamily of more than 5000 species in about 130 genera. The group is by far most diverse in tropical regions but northern temperate areas are well-represented; about 350 species occur in North America and the European fauna includes about 310 species and subspecies. The common name refers to the larval habit of modifying a covering of frass and organic matter applied to the egg by the female into a protective case which it will maintain over its lifetime and ultimately modify into a cocoon in which it will pupate.
The group is now usually divided into between three and five tribes although two of these were formerly classified as distinct subfamilies and others may be found in some works. Fulcidacini Gressitt, 1946 includes about 400 species in 11 genera, it is a predominantly Neotropical group with about 35 species occurring in North America and only 4 species of a single genus occurring in Asia. Fulcidacini species are commonly known as Warty leaf-beetle as they typically have roughened or densely tuberculate bodies and resemble avian or larval droppings. Clytrini Lacordaire, 1848, also formerly classified as a subfamily, includes more than 1300 species in 62 genera and 6 subtribes. They occur in all the major regions and are most diverse in South America, Asia and Africa, they are very poorly represented in Australia and are absent from many islands including New Zealand. Four of these subtribes are restricted to the New World; Babiina Lacordaire, 1848 and Megalostomina Lacordaire, 1848 are widespread, Arateina (3 spp.) is endemic to Argentina and Brazil, and Ishciopachina Chapuis, 1874 (2 spp.) occurs from Mexico to Argentina. Eoclytrina Monros, 1958 is endemic to Africa. Clytrina is a predominantly Old World group; of the 40 or so genera only 2 occur in the New World, including 7 species of Smaragdina Chevrolat in Dejean, 1836, the only genus within the subtribe to have a near-cosmopolitan distribution. The greatest diversity is in tropical regions and more than a quarter of all genera are endemic to Africa. Cryptocephalini Gyllenhal, 1813 is the largest tribe with more than 3500 species in 54 genera and 5 subtribes. Achaenopina Clavareau, 1913 is endemic to southern Africa while Stylosomina Chapuis, 1874 includes about 30 described species of the single genus Stylostomus Suffrian, 1848 and is restricted to the Palaearctic region and the Mediterranean area in
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Cryptocephalus coryli underside
particular. The remaining subtribes, Pachybrachina (10 genera), Monachulina (16 genera) and Cryptocephalina (21 genera) are present throughout the world. The tribe includes some very large and widespread genera which are well-represented in northern temperate regions. Pachybrachis Dejean, 1836 is a worldwide genus of more than 360 species in 2 subgenera; about 200 occur in the New World and of these about 150 are Nearctic while the Palaearctic fauna includes 150 species, about 45 of which have been named in the last decade, and 60 occur in Europe. With more than 1700 species Cryptocephalus Muller, O.F., 1764 is the largest genus, it occurs worldwide and is most diverse in tropical regions but about 80 species occur in North America and 196 are listed as European.
The European fauna is diverse although the majority occur in warmer southern regions. Cryptocephalini includes the two most speciose European genera, Cryptocephalus and Pachybrachis, and is otherwise represented by 12 species of Stylostomus. The UK fauna includes 20 species of Cryptocephalus although C. exiguus Schneider, 1792 has not been recorded since 2000 and C. violaceus Laicharting, 1781 was last recorded in the mid-nineteenth century, only a few of our species are at all common and widespread and most are local and rare or very rare. The European Clytrini includes about 110 species in 11 genera. By comparison the UK fauna is rather poor; of the 34 European species of Labidostomis only one, L. tridentata (Linnaeus, 1758), is listed as British but it was last recorded in the 1950s and is probably now extinct here. Twelve species of Clytra Laicharting, 1781 are listed as European but only one, C. quadripuncata (Linnaeus, 1758) occurs here, another persists on our list but has not been recorded since the 18th century. Smaragdina Chevrolat in Dejean, 1836 includes 18 European species of which two occur very rarely in the UK.
Members of this subfamily display complex biology both as adults and larvae. Adults are typical of the family, they are diurnal and feed on pollen, flower parts or leaves, most are monophagous or oligophagous on a range of herbaceous and woody plants and most occur over a relatively short season during the spring and early summer. Mating occurs on flowers or host foliage early in the season and oviposition occurs over a protracted period; to oviposit the female leans forward on her fore and middle legs and holds the egg with her hind legs as it is produced, the egg is then rotated against a depression in the fifth abdominal ventrite and coated with a mixture of secretions and faeces to form a protective shell, this process may take up to half an hour after which the encased egg is dropped to the ground (this is why they are called drop-beetles in some parts of the world). Here it seems the female is working carefully to achieve a precise appearance and in many instances the enclosed egg resembles a small seed-pod. In some species, notably among the Clytrini, the eggs may be collected by ants and taken into the nest or deposited among nest material, the female may facilitate this by dropping eggs from foliage overhanging a nest, and in many cases there is host specificity e.g. our UK species Clytra quadripunctata deposits eggs close to nests of the wood ant, Formica rufa L. In such cases the larva will modify its egg casing into a tough protective coat and feed on plant detritus and ant excreta within the nest, developing over the summer and following winter and pupating within a modified case in the spring. Myrmecophilous behaviour has also been recorded in other groups within the subfamily, including possibly some Cryptophagus, but the majority feed either openly on foliage, on fallen plant material or among leaf-litter, less commonly they feed on lichens growing on bark or rocks, freshly developing bark, fruits or seedlings. Larvae are usually longer than their protective cases and so they remain curved or folded inside, modifying the case as they grow; development may take up to three years but many temperate species are univoltine. When fully grown the larva will attach its protective case to a twig or trunk, the ground or a fallen leaf etc. and seal itself inside to pupate. In many cases it is not known at which stage they overwinter but adults emerge during spring or early summer.
Members are small to medium size beetles, 0.8-11.0mm, the majority will be recognized by a very characteristic appearance; elongate, rather parallel-sided and convex, sometimes almost cylindrical although commonly flattened dorsally, generally 1.5-2X longer than wide, rarely longer and in some tropical species almost quadrate. In many species, especially among the Cryptocephalini, the head is not, or only very narrowly, visible from above, hence the subfamily name, crypto-hidden, and cephalic-head. Colour varies widely and while some groups are mostly drab, grey or black and only weakly metallic e.g. in Fulcidacini, the majority are at least in part brightly coloured; in some e.g. some Labidostomis or Lachnaia, the body is bicoloured with pale elytra and dark forebody, others are bicoloured with patterned elytra e.g. many Clytra but more generally they range from entirely pale yellow, red, green or black to elaborately patterned throughout and many are partly or wholly metallic. The majority are glabrous and shiny but some e.g. Lachnaia, are distinctly pubescent. Head not declined; short, flat anteriorly and variously inserted into the prothorax, eyes entire, finely faceted and very variably convex, vertex and frons usually smooth and finely punctured, rarely with impressions, frontoclypeal ridge variable and sometimes absent, clypeus usually trapezoidal, labrum quadrate or nearly so and usually near-truncate anteriorly. Antennae inserted anteriorly, the insertions often not visible from above, 11-segmented; in Cryptocephalini long and filiform, in Clytrini short and variously serrate, highly modified in Fulcidacini; with a distinct scape and variously thickened apically. Pronotum transverse to quadrate, widest at or near the base and narrowed to a flat or rounded anterior margin, lateral margins curved or weakly sinuate and with or without a border, only rarely narrowly explanate. Pronotal disc smoothly convex, there may be impressions towards the basal margin but otherwise without sculpture, surface usually smooth and finely punctured. Scutellum very variable, in some cases apparently absent. Elytra generally much longer than the pronotum and at least as wide across the base, laterally near-parallel sided or weakly dilated apically, with well-developed epipleura that continue beyond the middle and variable apical margins, from truncate or separately rounded to continuously rounded; separately rounded apices often expose pigmented or metallic tergites. Elytral sculpture varies from smooth and very finely punctured, randomly and densely to sparsely punctured or each may have between 8 and 10 punctured striae which often fade in the apical half but may continue to the apex. In Fulcidacini the entire body may be very strongly and elaborately sculptured. The majority of species are fully-winged and many are known to be strong fliers. Abdomen with six tergites and five free ventrites, the basal tergite usually much longer than the second and often as long as 2-4 combined, fifth ventrite in female with a variable apical depression, unmodified in the male. Legs robust and moderately long to very long, often displaying various sexually dimorphic characters such as thickened or elongate front and middle femora, curved, dilated or elongated tibiae and dilated or in some cases greatly elongated tarsi. Pro-coxae round, variously projecting and separated by a prosternal process, meso-coxae transverse and convex, meta-coxae transverse and more flattened. Coxae and femora separated by an elongate trocanter which usually has a strongly oblique attachment to the femora, tibiae often with longitudinal ridges or grooves externally or internally and with or without terminal spurs. Tarsi 5-segmented, usually with the third dilated and concealing the tiny fourth segment, but other segments may also be dilated, in general those of the male are wider than those of the female. Claws simple to appendiculate or strongly bifid and usually without a visible empodium.