Pasaulyje daugiau kaip 37 tūkst. rūšių, Lietuvoje – apie 300. Vabalai vidutinio dydžio arba smulkūs, dažniausiai ovališkos formos. Nugara iškili, kūno apačia plokščia. Antenos karoliškos, visuomet nukreiptos pirmyn. Kojos trumpos, letenos su tankiai plaukuotais padais. Lapgraužių spalva labai įvairi, dažniausiai metalo žvilgesio. Kiaušinėlius prilipdo prie augalų lapų ar deda juos į dirvą. Kartais juos užmaskuoja pridėtinių liaukų išskyromis. Lervų kūno forma įvairi, dažniausiai su spalvotų karpelių eilėmis. Lapgraužiai ir jų lervos apgraužia įvairių augalų lapus, kai kurios rūšys pavojingos žemės ūkio kultūroms.
With over 37,000 currently known species in more than 2,500 genera, it is one of the largest and most commonly encountered of all beetle families. Adult and larval leaf beetles feed on all sorts of plant tissue.
Adults of leaf beetles are small to medium-sized, i.e. most species range from 1.0 to 18 mm in length, excluding appendages. The bodies of most species are domed, and oval in dorsal view (though some are round or elongated), and they often possess a metallic luster or multiple colors. In most specimens, the antennae are notably shorter than head, thorax, and abdomen, i.e. not more than half their combined length. The second antennal segment is of normal size (which differentiates leaf beetles from the closely related longhorn beetles). In most species, the antennal segments are of a more or less equal shape, at most they gradually widen towards the tip, although some Galerucinae in particular have modified segments, mainly in males. The first segment of the antenna in most cases is larger than the following ones. The pronotum of leaf beetles varies between species. In most, it is slightly to highly domed and trapezoidal to rounded-squarish in dorsal view. In some subfamilies such as the Cassidinae and to a lesser extent the Cryptocephalinae, the head is covered by the pronotum and thus not visible from above. The first three sternites are not fused, instead being linked by mobile sutures. Most species possess wings, although the level of development and thus flight ability varies widely, including within a single species, and some are flightless with fused elytra.
Most of the text below is from now defunct site www.ukbeetles.co.uk, where it was published under a CC BY 4.0 License.
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.
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.
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, 1-20 mm 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.
