The insects of the beetlefamilyChrysomelidae are commonly known asleaf beetles, and include over 37,000 (and probably at least 50,000)[citation needed]species in more than 2,500genera, making up one of the largest and most commonly encountered of all beetle families. Numeroussubfamilies are recognized, but the precise taxonomy and systematics are likely to change with ongoing research.
Leaf beetles are partially recognizable by theirtarsal formula, which appears to be 4-4-4, but is actually 5-5-5 as the fourth tarsal segment is very small and hidden by the third.[2] As with many taxa, no single character defines the Chrysomelidae; instead, the family is delineated by a set of characters.[3] Some lineages are only distinguished with difficulty fromlonghorn beetles (familyCerambycidae), namely by theantennae not arising from frontaltubercles.
Adult andlarval leaf beetles feed on all sorts of plant tissue. Many are serious pests of cultivated plants, for example theColorado potato beetle (Leptinotarsa decemlineata), theasparagus beetle (Crioceris asparagi), thecereal leaf beetle (Oulema melanopus), themustard beetle (Phaedon cochleariae) and variousflea beetles, and a few act as vectors ofplant diseases. Others are beneficial due to their use inbiocontrol of invasive weeds. Some Chrysomelidae are conspicuously colored, typically in glossy yellow to red or metallic blue-green hues, and some (especiallyCassidinae) have spectacularly bizarre shapes. Thus, they are highly popular amonginsect collectors.
Theimagos of leaf beetles are small to medium-sized, i.e. most species range from 1.0 to 18 mm in length, excluding appendages, with just a few larger species such asAlurnus humeralis, which reaches 35 mm. 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. Thepronotum 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.[4]
Until recently, the subfamily Bruchinae was considered a separate family, while two former subfamilies are presently considered families (Orsodacnidae andMegalopodidae). Other commonly recognized subfamilies have recently been grouped with other subfamilies, usually reducing them to tribal rank (e.g., the formerAlticinae,Chlamisinae,Clytrinae, andHispinae). The extinct subfamilyProtoscelidinae, containing fossils described from the Middle to LateJurassicKarabastau Formation, Kazakhstan, has been transferred to the familyAnthribidae.[5]
Chrysomelidae in general are herbivorous. Adults mostly feed on leaves and flowers ofangiosperm plants, while larval diets are diverse.[6]
Bruchinae larvae are seed-borers, usually in seeds oflegumes. Many adults feed onpollen, not necessarily that of the larval host.[7] Some do not feed as adults.[8]
Cassidinae larvae may beleaf miners (many of the former Hispinae),stem borers (e.g.Estigmena) and external leaf feeders (e.g.Leptispa,Oediopalpa).[9]
Chrysomelinae generally feed on leaves as adults and larvae, though some species feed on flowers instead.[10]
Criocerinae larvae are usually leaf miners or feed externally on leaves.[9] Some species aregallers instead.[11]
Most Cryptocephalinae larvae live and feed inleaf litter, making themdetritivores, while a few feed on green leaves.[12] Some Cryptocephalinae have larvae that live in ant nests (myrmecophily), where they feed on dead plant or even dead animal matter.[13]
The semi-aquatic Donaciinae have larvae feeding on the sap of roots of aquatic plants. In addition to food, they also obtainoxygen this way, from the plant's intercellular spaces. Adults feed on leaves of aquatic plants.[14]
Galerucinae are quite varied, with larvae living in soil and feeding on rootlets (e.g.Aulacophora,Cerotoma,Diabrotica), mining leaves (someMonoxia) or feeding externally on plants (e.g.Arima,Galeruca,Galerucella).[9]
Lamprosomatinae larvae feed on green plant parts or graze on bark.[15]
Sagrinae larvae mostly form galls in stems of shrubs,[9] thoughMecynodera balyi instead feeds inside seed pods ofPandorea vines.[16] Adults feed on pollen.[17]
Synetinae larvae feed on roots, mainly of trees in cold northern forests.[9]
To be able to digest the plant matter, the beetles use enzymes likepectinases. This group of enzymes are either produced by the beetles themselves, due tohorizontal gene transfer, or symbiotic bacteria provides them with the enzymes. But both solutions are never used simultaneously.[18]
A Finnish researcher published an exhaustive paper describing the natural enemies of the alder leaf beetlePlagiosterna aenea and other species of leaf beetles observed in the field.[19] Predators of chrysomelid eggs include true bugs such asAnthocorus nemorum andOrthotylus marginalis.[20] Hoverflies (e.g.Parasyrphus nigritarsis) sometimes lay eggs adjacent to beetle egg clutches and when the fly larva hatches it consumes beetle eggs and young larvae.[20] Larval predators includeA. nemorum, the bugRhacognathus punctatus,[20] and the waspSymmorphus bifasciatus.[21] Some species of wasps, such asPolistes carolina, have been known to prey upon Chrysomelidae larvae after the eggs are laid in flowers.[22] Adult beetles are consumed byR. punctatus.[20] More information about natural enemies can be found in the articles about the chrysomelid beetlesChrysomela aeneicollis,Phratora laticollis andPhratora vitellinae.
^Jolivet, Pierre; Verma, Krishna K. (2002).Biology of Leaf Beetles. Andover: Intercept. pp. 5–9.ISBN1-898298-86-6.
^Stresemann, Erwin (1994).Exkursionsfauna von Deutschland. Wirbellose Insekten. Erster Teil (8th ed.). Jena: Gustav Fischer Verlag.ISBN3-334-60823-9.
^Legalov, A.A. (2013). "Review of the family Anthribidae (Coleoptera) from the Jurassic of Karatau: subfamily Protoscelinae. GenusProtoscelis Medvedev".Paleontological Journal.47 (3):292–302.doi:10.1134/S0031030113030064.S2CID83960406.
^Kanervo, V. (1946). "Tutkimuksia lepän lehtikuoriaisen, Melasoma aenea L. (Col., Chrysomelidae), luontaisista vihollisista. (Ref.: Studien über die natürlichen Feinde des Erlenblattkäfers,Melasoma aenea L. (Col., Chrysomelidae)".Annales Zoologici Societatis Zoologicae Botanicae Fennicae "Vanamo".12 (3):1–202..
^abcdRank, N. E.; Smiley, J. T.; Köpf, A. (1996). "Natural enemies and host plant relationships for chrysomeline leaf beetles feeding on Salicaceae". In P. H. Jolivet; M. L. Cox (eds.).Chrysomelidae Biology. Vol. 2: Ecological Studies. Amsterdam: SPB Publishing. pp. 147–171.
^Blüthgen, P. (1961).Die Faltenwespen Mitteleuropas (Hymenoptera, Diploptera). Berlin: Akademie Verlag.
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