CHRYSOMELIDAE Latreille, 1802

Leaf Beetles

Includes many widespread and common species, which occur on a wide range of plants in most habitats. Adults are present throughout the year and may be sampled from tussocks etc. through the winter.

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POLYPHAGA Emery, 1886

CHRYSOMELOIDEA Latreille, 1802

9

Approx. 65

Approx. 280

1.1-18mm

Around the World

This is a very large and enormously diverse family which includes almost 40000 described species in more than 2500 genera, numerous tribes and about 15 subfamilies although these are likely to change in both scope and rank as research proceeds. The common name refers to their almost exclusively phytophagous feeding habits, adults and larvae consume all types of plant tissue, and as many species regularly generate large populations some have become serious horticultural or agricultural pests e.g. the asparagus beetle, Crioceris asparagi (Linnaeus, 1758) or the notorious Colorado beetle, Leptinotarsa decemlineata (Say, 1824). On the other hand many species have been used as biocontrol agents of invasive weeds, often far from their natural range and often to combat adventive plant species. Many groups are quite distinct and so have earned their own common names. Bruchinae Latreille, 1802 includes the pea and bean weevils, so called because the adults are variously rostrate. They are mostly small species strongly associated with peas, beans and vetches. Several species infest stored grain and lentils etc, and can be extremely destructive. Living among essentially limitless food and generally good conditions of temperature and humidity etc. they can produce huge continually brooded populations in domestic and commercial premises. Cassidinae Gyllenhal, 1813 is a very large and diverse group but is generally referred to as tortoise beetles after a subgroup of rounded and flattened species. Chrysomelinae Latreille, 1802, the broad-bodied leaf-beetles, characterize much of the family with their convex and broadly-oval form. Cryptocephalinae Gyllenhal, 1813 remains a poorly defined group which includes some former subfamilies as tribes, due to the egg-laying habits of some genera they are often referred to as pot-beetles. Donaciinae Kirby, 1837 includes the distinctive reed-beetles. Galerucinae Latreille, 1802 includes the Alticini Newman, 1834 or flea-beetles. The very distinctive Sagrinae Leach, 1815 are known as frog-legged beetles or, as they mostly occur in Australia, Kangaroo beetles. By far the most diverse group is Galerucinae followed by Cassidinae, Eumolpinae, Bruchinae, Cryptocephalinae, Chrysomelinae and Criocerinae, the remaining subfamilies comprising only a small proportion of the family.

Ecology

Chrysomelid life-cycles in temperate climates are generally univoltine with eggs laid in the spring or early summer, rapidly developing larvae and new generation adults a little later in the year. A minority will oviposit in the autumn and the eggs will overwinter to produce spring larvae, and in warmer regions adults will emerge from spring pupae, feed, and then aestivate before producing eggs, often in tough egg cases, in the autumn that will overwinter. Many species overwinter as adults in the soil or among litter and tussocks although some root-feeding species will overwinter as late-instar larvae and continue their development in the spring. Both adults and larvae feed on a very wide range of monocotyledons and dicotyledons as well as Bryophytes and horsetails. Some, although only a few in temperate regions, are myrmecophilous during certain developmental stages. Bruchid larvae develop within the seeds of Fabaceae, consuming the starch or developing cotyledons while the adults consume the pollen of a range of plant families. In general the adults of most Chrysomelids feed upon the leaves and developing stems of plants, they often attack flower parts but only seldom feed on pollen. Larvae feed on all parts of plants, most often exposed on the leaves and, because of the adult egg-laying habits, they will often occur in numbers and so the feeding damage is obvious. Some feed within leaves or stems and produce characteristic mines, while others develop in roots. Eggs are generally laid among foliage or on or within stems or flowers although many species deposit them in the soil below the host plant, especially where they will produce root-feeding larvae, they develop rapidly and larvae hatch within a week or two. Under some conditions, and with autumn-laid eggs, they may diapause and hatch after an extended period.  Ovoviviparity occurs in some species where the larvae are well-developed at the time of oviposition and hatch soon after, while some are viviparous, producing small larvae that will immediately disperse and commence feeding. These strategies have developed to overcome adverse conditions e.g. a short season or a high likelihood of predation or parasitism. The number of larval instars is usually small with the majority passing through three, but four to six is not unusual. They generally develop rapidly and this stage is often passed within weeks during spring or early summer. Pupation may occur on or within various parts of the plant but most larvae descend into the soil beneath the host and construct an earthen pupal cell, and bruchids pupate directly within the host seed. The adults of many species are short-lived although they may have a long season when mating and egg-laying continue over several months and new generation adults eclose while the previous generation are still extant. In many cases there will be mating pairs and gravid females throughout the season and very large populations will occur. The presence of completely skeletonised plants in early summer is a frequent reminder of this. Almost needless to mention that leaf beetles may be found frequenting plants in general in a very wide range of habitats and many are arboreal and either sub aquatic or truly aquatic. Sweeping vegetation, searching flowers and observing generally will produce specimens, during the winter many adults will occur among litter and tussock samples and may be found under bark or debris in general, many species will overwinter in large groups, alternating between overwintering sites and spring and summer areas where they feed and reproduce and develop. Most species are fully-winged and fly well. Host plant associations are generally well known, especially within familiar faunas such as those of most developed countries, and more so as many genera include pest species, and while building a reference collection many of these will soon become understood.

Sagra ferox Baly, 1877

Description

As noted above the morphological variation is huge and so the brief description that follows will necessarily fail to portray the almost fantastic morphology seen in many tropical forms, to compensate for this, at least partly, further accounts of some of the groups are given either below or elsewhere on the site. There is no single defining character or even convenient series of defining characters for the group; some subfamilies are often considered as distinct families e.g. Orsodacnidae Thomson, C.G., 1859 and Megalopodidae Latreille, 1802, and some species are very similar to the cerambycids, but chrysomelids may be, at least substantially, recognized by the pseudotetramerous tarsi; 5-segmented but with the fourth segment small and often obscured within the lobes of the third although in some groups they are truly four-segmented as the fourth and fifth are fused, and the antennae which are 11-segmented, rarely 10-segmented, and  moniliform, filiform, serrate or pectinate; sometimes gradually thickened but never distinctly clubbed, and not inserted on tubercles in front of the eyes or held back over the body as in many cerambycids. Adults of most species are small to medium sized, 1-20mm although there are many tropical groups e.g. Sagrinae or species of the Neotropical genus Alurnus Baly, 1869 which exceed this. Many species of all subfamilies are brilliantly coloured and patterned and many are metallic, being conspicuous and striking in the wild and so ‘easily’ collected which has made the group a perennial favourite with collectors. In most groups the head, pronotum and elytra are free and well-defined but in some they are closely fitting and the outline is continuous e.g. Cryptocephalus Geoffroy, 1862 and Oomorphus Curtis, 1831. The head may be prognathous, hypognathous or opisthognathous and in some groups e.g. Cassidinae Gyllenhal, 1813 and Cryptocephalini Gyllenhal, 1813 it is hidden under or mostly within the thorax. The basal antennomere is larger than the others and the following segments tend to be similar in shape and size; in cerambycids the second segment is usually much  smaller than the first  and third, and  they are short or  of medium

length, generally not exceeding the body length and usually much shorter. In some groups e.g. within the Galerucinae, they are sexually dimorphic, being modified in the male, and in general those of the male are longer. Most species are diurnal and have well-developed eyes. The pronotum is very variable, mostly convex and transverse to quadrate with distinct lateral borders and only weakly explanate but there are some spectacular exceptions, especially within the Cassidinae, the surface sculpture is generally poorly developed with various punctation and lateral grooves but may be strongly developed as in some Hispini Gyllenhal, 1813 (Cassidinae). The elytra are similarly very variable, usually entire, covering the abdomen and separately rounded although in the Bruchinae they are truncate and expose several abdominal segments. The form is usually convex and oval to very broadly oval, almost circular in many instances, and the surface varies from smooth to finely or coarsely and randomly punctured to striate with small or largely punctured striae and interstices, longitudinal carinae or other sculpture. In the ‘tortoise beetles, they are very broad and generally, although there are exceptions, widely explanate with well-developed puncture-like sculpture and longitudinal ridges or depressions. In a few flightless groups they are fused, the genus Timarcha Samouelle, 1819 typifies this; here the hind wings are generally missing altogether. In some Hispini the elytra are strongly sculptured as the pronotum. The abdomen generally has five visible sternites. In larger species the legs are robust and often well-developed, in smaller species they tend to be rather weakly sclerotized, in the Alticini the hind femora are developed for hopping and in Bruchids they bear various teeth. In some tropical species the forelegs are greatly enlarged and all legs may be modified and/or sexually dimorphic. In some groups there are grooves on the ventral surface for the retraction of the legs. The claws tend to be well-developed, generally free and simply pointed but in some cases connate, toothed or lobed at the base or bifid. The family includes many large genera, species of which will need to be dissected, Longitarsus Berthold, 1827 and Altica Geoffroy, 1762 are good examples from the U.K. but further afield genera including larger species such as Chrysolina Motschulsky, 1860 will also need to be dissected. For many years only the males could be dealt with in this way but now more and more keys include spermatheca so allowing females to be identified.

CHRYSOMELIDAE in the UK
Altica lythri 1.jpg

A key to the UK subfamilies can be found HERE.

In order to keep this page manageable a more detailed discussion of the various subfamilies can be found through the links above. The following is a brief introduction to the U.K. fauna, and much more can be found by following links to the individual species pages or through the index.

The U.K. Chrysomelidae fauna can be characterized by the following brief description: 1-18mm, convex and broadly oval to elongate or widely dilated and rather flat, discontinuous in outline except for Cryptocephalus Geoffroy, 1762, Oomorphus Curtis, 1831, Cassidinae Gyllenhal, 1813 and various Alticini Newman, 1834. Entirely black to variously coloured, patterned, or metallic. Antennae 11-segmented, 10-segmented only in Psylloides Latreille, 1829, filiform to serrate or moderately thickened towards the apex but never distinctly clubbed, mounted on the front of the head before the eyes and above the mandibles, never on tubercles or in pits. Eyes round to oval and generally entire, weakly emarginate in Criocerinae Latreille, 1804, strongly so in Bruchinae Latreille, 1802. Pronotum quadrate to transverse, unadorned and often broadest at the base, generally with lateral borders but sometimes e.g. Criocerinae, Donaciinae Kirby, 1837 and Cassidinae without, sometimes with lateral or basal grooves. Scutellum visible. Elytra very variable; completely covering the abdomen except in Bruchinae and gravid females of many species, smooth to randomly punctured or distinctly striate, and with the exception of the Cassidinae they are mostly only narrowly explanate. Legs relatively long, mostly unadorned but the femora may be toothed e.g. in Donaciinae and Bruchinae, or expanded e.g. Alticini. Tarsi 5-segmented; the third segment bilobed but occasionally others as well e.g. in Timarcha Samouelle, 1819. Nine subfamilies are included on the UK list.

 

  • Bruchinae includes 9 native species and about 6 introduced and more or less established synanthropic pests of foodstuffs etc. and others are occasionally imported. Adults are very distinctive and range from 1.7-5.3mm in length. Several become abundant in the wild from late April or May and remain so into July. They oviposit in developing seed pods of Fabaceae where the larvae will develop. Synanthropic pest species may be continuously brooded. They are easily sampled in the wild by sweeping suitable vegetation and some e.g. Bruchus rufimanus Boheman, 1833 will be found in large numbers.

  • Donaciinae includes 21 species in 3 genera, commonly known as reed beetles, they are all very characteristic species found by sweeping marginal vegetation. 5-12mm.

  • Criocerinae includes 8 species in 4 genera; they are characteristically elongate and flattened.  All are medium sized, 3-8mm with the head transverse and visible from above; they have prominent convex eyes and long antennae. The pronotum is narrower than the elytra and never bordered laterally. The elytra are long, parallel-sided and completely cover the abdomen, and all have regularly punctured striae. All are brightly coloured. The group includes various pest species e.g. the asparagus beetle, the lily beetle and the cereal leaf beetle.

  • Lamprosomatinae Lacordaire, 1848 is represented by the single species Oomorphus concolor (Sturm, 1807). It is a small, 2-3mm compact-oval and shiny black species, often with a bronze reflection, with dilated tibiae and expanded apical antennal segments. This unmistakable species occurs across the south and may be found by beating ivy.

  • Cryptocephalinae includes 25 species of 4 genera. They are small to medium-sized beetles, 2-8mm, parallel-sided and convex with the head mostly hidden from dorsal view. Most are brightly coloured and many are patterned or metallic. Cryptocephalus Geoffroy, 1762 includes 20 species, a few of which are common and widespread. Labidostomus tridentatus (Linnaeus, 1758) is now very probably extinct. Smaragdina Dejean, 1836 are very rare and of our two species of Clytra Laicharting, 1781, C. quadripunctata (Linnaeus, 1758) is widespread but very local, generally occurring alongside wood-ants, the other, C. laeviuscula Ratzeburg, 1837, is thought to be long extinct in the U.K. Species will be found by beating and sweeping trees, shrubs and vegetation in a wide variety of habitats.

  • Eumolpinae Hope, 1840 includes a single species, Bromius obscurus (Linnaeus, 1758). It is a recent addition to the U.K. list and is known from a few sites in the midlands.

  • Chrysomelinae Latreille, 1802 includes 45 species in 11 genera. Includes our most striking species as many are large and brightly coloured and they will soon become familiar in the field. They are characterized by the widely placed antennae mounted above or outside the base of the mandibles and close to the margin of the eyes. The hind femora are never dilated compared to the others. Includes several agricultural or horticultural pests e.g. the rosemary beetle and the occasionally introduced Colorado beetle. Many are common and widespread and will be found associated with the host plants, most are fully-winged and disperse by flight although our two species of Timarcha are wingless. Several species are very local e.g. the northern Scottish Phratora polaris Schneider, J.S., 1886, rare or thought to be extinct e.g. Chrysomela tremula Fabricius, 1787, while several are very recent introductions e.g. Chrysomela saliceti Suffrian, 1851 or the Tasmanian Eucalyptus feeder Paropsisterna selmani Reid & de Little, 2013.

  • Galerucinae are distinguished from the other subfamilies by the antennae being placed close together inside the base of the mandibles. The antennae are 11-segmented except in Psylliodes where they are 10-segmented, and generally long, sometimes very much so e.g. in Luperus Geoffroy, 1762 and some Longitarsus Berthold, 1827. The subfamily is divided into two very distinct tribes. Alticini is the most diverse of the U.K. leaf-beetle tribes with 22 genera and about 125 species, and is distinguished by the enlarged hind-femora. Commonly known as flea beetles due to their ability to hop powerfully when disturbed, many are widespread and common and will occur when sweeping vegetation generally, many are stenophagous and so knowledge of the host-plants is an advantage both when collecting and identifying. Some genera e.g. Longitarsus and Altica Geoffroy, 1762, are difficult to identify and many will need to be dissected. Many species produce very large populations in the summer and some have become agricultural pests, and many of the larvae are root-feeders. The Galerucini Latreille, 1802 includes 20 species in 11 genera and all have the femora more-or-less equal in size and are incapable of hopping. They vary widely in morphology, from convex and oval e.g. Agelastica Dejean, 1836, to elongate and flattened e.g. Luperus. The majority are rather drab although Sermylassa halensis (Linnaeus, 1767) is spectacularly coloured and metallic. Host plant preferences are rather specific and generally well-known and so knowledge of this is an advantage when sampling.

  • Cassidinae includes 14 species in 3 genera. They are very distinctive in form; broad and flat with the head and ventral surface hidden in lateral view. Of the 12 species of Cassida Linnaeus, 1758, several are widespread and common; they are generally polyphagous with a preference for a few plant species e.g. the common and widespread C. vibex Linnaeus, 1767 and C. rubiginosa Muller, O.F., 1776 will usually be found on thistles while the local C. viridis Linnaeus, 1758 is associated with various mints. The very distinctive Pilemostoma fastuosa (Schaller, 1783) is a very rare species of southern England and Wales while Hypocassida subferruginea (Schrank, 1776) is known only from nineteenth century records and is presumed to be long extinct.

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