Around the World

The Neotropical fauna is probably less well understood than most but is still the most diverse in terms of genera if not species with about 550 species of 220 genera (and it is unusual in world-terms in having Hispinae and Cassidinae predominant among the chrysomelid fauna), the majority of these are endemics and non-endemics are generally members of large and very widespread genera such as the well-known Chaetocnema and Longitarsus, furthermore the greatest diversity of non-endemics tends to be in Central America and falls-off rapidly in South America e.g. 48 species of Longitarsus occur in Central America while only 8 occur in Brazil. The region includes some large endemic genera e.g. Alagoasa Bechyne, 1955 (with about 150 spp.) as well as large groups of related genera e.g. the endemic ‘tribe’ Monoplatina includes almost 600 species of more than 40 genera. The Nearctic fauna, by contrast, includes almost 500 species of about 50 genera. Only a few Nearctic genera are endemic and about one third are of Neotropical origin, 19 genera (or about 40% of the total) are also represented in the Palaearctic, Oriental and African regions.

​

With more than 100 genera the Oriental region is second only to the Neotropics and only slightly more diverse than the African region, of these about 60 are endemic to India and about 20 occur on the southern islands, the fauna of southern India and Sri Lanka (which alone includes at least 10 endemic genera) form a unique group that seems to be related to the fauna of Malaya, Thailand and Myanmar. The Oriental fauna is notable for the large number of flightless species and includes genera with only apterous species. The Australian fauna is the smallest of all the major world regions and includes only a small proportion of endemic species and groups and some genera are notably missing e.g.  Dibolia Latreille, 1829 (60 spp.) or Blepharida Chevrolat, 1837 (60 spp.) occur worldwide except for Australia. The majority of Australian genera are also represented in the Oriental and African regions or further afield. The African region, including Madagascar, includes about 1600 species of more than 100 genera, many of which are also represented in the Oriental and Palaearctic regions but the region includes many endemics, of the 84 genera of sub-Saharan Africa about 65% are endemic and of the 58 genera in the Southern Afrotropical area about 12% are endemic. Madagascar has 10 endemic genera and a further 13 which are otherwise restricted to mainland Africa, and even the Seychelles host 2 endemic genera.

​

The Palaearctic region is rather poor in genera (about 65) but is very rich in species (about 2400) although the number of endemic genera is small and these are mostly distributed in Mediterranean areas, the Caucasus and mountain regions of southern Europe. While the region is rich in species the fauna includes only a few endemic genera and most genera of the adjacent Oriental and Afrotropical regions tend to be missing or represented by only a few species at the extreme north of their range, and if these overlapping genera are allowed for the temperate Palaearctic fauna is roughly equal, in generic terms, with that of the nearctic region. The UK fauna is fairly representative of that of Europe as a whole; of the 32 European genera 21 (about 66%) extend to the UK, and in terms of gross morphological diversity a knowledge of our fauna will provide a good overview of that of the Holarctic and will allow much of the world fauna to be recognized. The UK fauna is considered briefly below.

​

Description

Typically small to medium-sized beetles with enlarged hind femora modified to provide a very powerful jump, hence the common name, and like true fleas the jump is so powerful that they seem to vanish before the eyes. 1.0-6.0mm, the majority of species between 1.5 and 4.5mm, many are elongate-oval and variously convex, sometimes very strongly so, and discontinuous in outline with the head narrower than the pronotum and the base of the elytra wider than the base of the pronotum. The group is very closely related to the Galerucinae but our UK fauna, while readily separated by the enlarged hind femora, tend to be distinct in general habitus, this does not apply to the wider world fauna where many Alticinae closely resemble galerucines but for the swollen femora. Colour varies widely, many are unicoloured black, brown, orange or yellow, with or without a metallic reflection, and bicoloured species, with the forebody and elytra contrasting, are common although not so much among our UK fauna, beyond this the group displays an incredible range of brilliant colours and patterns, more especially so in the tropics but certain temperate groups are just as striking e.g. members of the New World genus Disonycha Chevrolat, 1836. Most species are glabrous or nearly so and any pubescence tends to be fine and short, either distributed across the body or arranged in lines along the elytral striae. Head generally hypognathous or oblique to the body axis and variously sunken into the prothorax, in rare cases hidden from above by the anterior pronotal margin, vertex simply convex, frons with various transverse or oblique furrows between the eyes and antennal insertions, clypeus very variable but often narrow and almost quadrate. Eyes usually well-developed and convex, commonly transverse or reniform but variable, punctation very variable often fine and sparse and so the head appears smooth. Antennae 10 or, usually, 11-segmented, long and filiform or weakly serrate, usually with all segments elongate and the second segment shorter than the others, inserted between the eyes and narrowly separated, at most by the length of the basal segment. Although the group has not developed ‘clubbed’ antennae, in some species e.g. in Mantura Stephens, 1831, the distal segments are gradually enlarged, in many antennal length is sexually dimorphic, and in some e.g. some Phyllotreta Dejean, 1836 the males have various segments enlarged. Pronotum widely transverse to slightly elongate, broadest at the base or about the middle and with distinct lateral borders, posterior angles distinct, anterior angles variable; often hidden from above or simply rounded and sometimes developed into a lateral tubercle or tooth, not or only rarely and then weakly explanate. Pronotal surface flattened to smoothly convex, in many genera with elongate basal fovea which may be joined by a transverse furrow n front of the basal margin, punctation very variable, most are glabrous or nearly so but a few species have short recumbent pubescence. Prosternum usually short in front of round or elliptical coxal cavities separated by a moderately wide process which is truncate or rounded apically and reaches the anterior margin of the mesosternum. Elytra very variable, strongly rounded, almost circular in outline, to parallel-sided, shoulders sloping to broad and strongly convex, epipleurs usually wide and strongly reflexed in the basal half and apical margin continuously rounded to acuminate. Elytral surface very variable in convexity, from hemispherical to flattened, often without striae and only very finely punctured, where present the striae vary from rows of fine punctures between broad and flat interstices to rows of very strong punctures that almost obliterate the interstices, the sutural stria is often abbreviated and striae may be regular or partly or substantially confused or the elytra may be randomly punctured, there may be impressions inside the shoulders or laterally toward the apices but otherwise they usually lack structure. Abdomen with five ventrites, the basal ventrite longest, usually sexually dimorphic with the hind margin of the apical ventrite incised in the male and smoothly rounded in the female. Legs usually well-developed and robust, the fore and middle femora only a little broader than the tibiae, the hind femora usually excavate internally toward s the apex to accommodate the tibiae when folded and massively developed to contain the internal jumping organ which consists of highly modified extensor and flexor muscles controlling the action of a metafemoral extensor tendon working against a tibial flexor sclerite, the effect when activated is to rapidly open the femoral-tibial joint, forcing the apex of the tibia to push down against the substrate and propel the beetle very rapidly upward or forward. Beyond this they can walk normally and most species are capable of flight. Front and middle tibiae usually simple but sometimes with one or more external teeth or excavate before the apical margin, apical spurs usually tiny or apparently absent. Hind tibiae long and variously straight to strongly sinuate externally or internally, usually extended into a sharp internal apical tooth and with a row or rows of stiff setae flanking an excavate external margin in the apical half or third, apical spur very variable. Tarsi pseudotetramerous, fore and middle tarsi normally developed, hind tarsi often with the basal segment much longer than the others, in most species the basal segment(s) of the fore and middle tarsi are broader than those of the female.

​

So far as the UK fauna is concerned identification to generic level is straightforward and many species in the smaller genera are easily identified but many of those in the larger genera such as Longitarsus, Aphthona or Altica will need to be dissected or identified by comparison with reference material. A good aid to specific identification can often be taken in the field by noting the plant from which a specimen was taken as many are monophagous or oligophagous.

​

Ecology

Apart from a few very recently discovered myrmecophilous species (a lifestyle known otherwise among the chrysomelids only from two genera of Cryptocephalinae), flea beetles are herbivores; species tend to be monophagous or oligophagous and genera tend to be restricted to a family or to a few closely-related families of plants, although many species are able to survive adverse conditions by consuming foliage of non-host species of plants, especially various trees and shrubs. For these reasons the group includes many notorious pests. The vast majority of temperate species are univoltine and undergo one of two general lifestyles, adults may overwinter and breed in the spring to produce larvae that develop through the summer and produce adults that will overwinter, or adults may breed in the summer and produce larvae that will develop in the present year, overwinter and complete their development in the spring and produce adults that will breed in the summer, and both strategies are common and others are known e.g. where larvae continue to develop into the winter and produce winter adults. In most cases eggs are laid into soil at or near the base of the host plants, less commonly they are laid on foliage, usually on the ventral surface of leaves and covered with protective secretions or frass by the female, in the case of leaf-miners the presence of such secretions may change the growth of the leaf, causing blisters on veins or epidermal tissue that the larva will exploit, and less often still they may be laid into tender stems of host plants. Most species have rather well-defined periods of mating and egg-laying but in some these are protracted over the warmer months and in a few species gravid females may be found year-round. Adults feed on foliage, in the vast majority of cases on herbaceous dicotyledons, more rarely on monocotyledons and less frequently still on various mosses, ferns, horsetails or conifers and many have been observes feeding on pollen. Most larvae undergo three instars, develop rapidly and feed within roots or stems or mine leaves, a few feed externally on foliage or roots and most pupate in the soil although many leaf-mining larvae pupate within the feeding galleries. Adults are generally associated with host plants and may be sampled by sweeping foliage etc, most are diurnal and will be found in numbers although during bad weather they tend to shelter in the soil and so may appear to be absent for many days, sweeping can be an ordeal as they can be very difficult to capture, especially when it is warm and they are active but sweeping at night is also very productive and here they are reluctant to hop away even under powerful torchlight and are easily tubed. Many species may be sampled with yellow pan traps and many will occur in flight-interception traps. During the colder months they will be found in tussock and litter samples and may be present in flood refuse. Pest species occur worldwide and several of the most important occur in the UK, they frequently achieve high densities and can be commercially damaging, in horticultural and agricultural situations they are usually controlled with traps or insecticides but in smaller operations the use of companion plants, intercropped to mask the scents of the host plants, and trap crops, plants also used by the beetles but commercially unimportant, can be effective in reducing damage. Numerous garden crops and ornamentals are attacked by flea beetles but the most damaging UK pest species include Psylliodes chrysocephala (Linnarus, 1758), a serious pest of oilseed rape and Brassicas, Aphthona euphorbiae (Schrank, 1781) which attacks flax and linseed as well as various fruits, Longitarsus parvulus (Paykull, 1799), the small flax flea beetle, and Phyllotreta undulata Kutschera, 1860, a worldwide pest of Brassicas and Chinese cabbage in particular. Phyllotreta also includes other species that, at least in recent years, are less serious pests e.g. P. Cruciferae (Goeze, 1777), the cabbage flea beetle, P. nemorum (Linnaeus, 1758), the turnip flea beetle, and P. vittula (Redtenbacher, 1849), the barley flea beetle. Most of our genera include common and widespread species, in the case of Longitarsus, Phyllotreta, Psylliodes, Aphthona, Altica and Crepidodera several species should soon be discovered by general sweeping, and once these have been identified and recorded it should be a simple matter of finding the host plants and searching for other species, in this way such species as Hermaeophaga mercurialis (Fabricius, 1792), Epitrix pubescens (Koch, 1803) and Podagrica fuscicornis (Linnaeus, 1767), among many others, will soon be found. Larvae may also be present on the hosts, either as miners as in e.g. Sphaeroderma or externally on the foliage e.g. Altica or Mniophila, those of Psylliodes chrysocephala feed within tender Brassica stems and are easily found by slicing the stems open, these can all be photographed and recorded or reared to work out the life-history.