SAGRINAE Leach, 1815
Frog-legged Beetles
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This, the smallest of the chrysomelid subfamilies, is probably most closely related to the Bruchinae, it is also closely related to the Donaciinae and Criocerinae and there is good evidence that these subfamilies belong in a distinct group, named tentatively as the sagrine clade. The number of genera remains contentious and provides endless delights when referring to older (and sometimes not so old) literature e.g. Rhagiosoma Chauis, 1878 should probably be referred to more correctly as Prionesthis Lacordaire, 1845, and this situation is very likely to change as research progresses, but at least 12 genera are generally accepted and about 70 species are known. Most occur in the Old World tropics although a single species is known from South America and 9 species of the genus Sagra Fabricius, 1792 are known from the Oriental region. Sagra is the largest and most widespread genus; it is the only genus to occur in Africa, where it is represented by about 35 species, although the Madagascan genus Rhagiosoma Chapuis, 1878 (which may actually include several genera and may also include a species in East Africa) includes 6 species. The greatest diversity is in Australia (they do not occur in New Zealand) where about 40 species of 11 genera are known and, with the exception of the widespread Sagra femorata (Drury, 1773), all of these are endemic. The majority of Australian species occur in dry regions of the north and west. The group is relatively poorly understood, partly because many species are very variable in size and colour and many varieties and forms have been named, some of these may turn out to be distinct species or some forms presently considered as distinct species may be merged, and partly because many species are restricted in distribution and in need of further study. On the other hand they are among the best known of leaf beetles because they are large, often brilliantly coloured and metallic, and males of some species have greatly enlarged hind legs - which gives rise to the common names - and which adds to their fascination. Despite the enlarged femora they do not jump. Many of these large and colourful species are collected mercilessly and sold for jewellery or trinkets or to collectors worldwide. Some spectacular species e.g. S. buqueti (Lesson, 1831) from Thailand and Malaysia, are now being bred in captivity and pupae are available to buy online. Framed series of the so called Giant Frog Beetle (Sagra longicollis Lacordaire, 1845) are widely available and, despite being expensive, very popular.
 Sagra femorata |
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The biology of the group is poorly understood although larvae and pupae of a few species of Sagra have been described and a few host plant associations are known. Plants of a wide range of families are known to be, or suspected to be, larval hosts but the situation is complicated because adults of many genera (but not Sagra) feed on a range of flowers. It is thought that each genus, or maybe a small group of genera, is restricted to plants of certain families e.g. Carpophagus MacLeay, 1827 and Diaphanops Schönherr, 1845 on Myrtaceae, and Atolasis Lacordaire, 1845 on Apiaceae and Malvaceae. Sagra are mostly associated with Fabaceae although a single species is known to cause galls in mangrove plants (Rhizophoraceae), and S. femorata is known to be widely polyphagous, attacking various species of plants. The genus Mecynodera Hope, 1840 includes species associated with Eleocarpaceae, Myrtaceae, Fabaceae and Xanthorhaceae as well as various herbaceous plants. Adults of most genera feed on flowers, including pollen, while those of Sagra feed on tender leaves and shoots. So far as is known most species mate and oviposit over a very long season and eggs are laid in groups, either in the soil or in earthen cells attached to host stems. Larvae develop in stems, they generally develop quickly and pupate in situ but there are exceptions; fully grown larvae of Mecynodera and Polyoptilus Germar, 1848 have been found in subterranean cells, and larvae of Atolasis is thought to pupate in the soil after emerging from its gall. Larvae of Mecynodera balyi Clark, 1864 are unusual; they are seed feeders, feeding inside the pods of vines (Pandorea Spach. Bignoniaceae) and, other than various Bruchinae, are the only chrysomelids known to do so.
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6-35 mm. Typically elongate and discontinuous in outline with a relatively small head, narrow pronotum and broad, near parallel-sided elytra. Body rather flattened to very convex. Legs long and usually very robust, often sexually dimorphic. In Sagra the body and appendages are often brightly coloured or bicoloured and strongly metallic, in other genera typically black, brown or yellow, often with lighter or darker markings. In most genera the body is glabrous or very sparsely setose although in Diaphanops it has dense decumbent pubescence. Head usually prognathous with strongly protruding eyes and well-impressed frontal furrows delimiting oblique and raised interocular or antero-ocular tubercles. Frontoclypeal suture well-developed to completely absent, clypeus sometimes produced into a short rostrum, labrum transverse and unmodified anteriorly. Antennae 11-segmented, filiform, though slightly serrate in males of some genera, and often with short or even quadrate basal segments, insertions placed in front of the eyes and visible from above. Pronotum weakly transverse to weakly elongate, widest across the base or behind the apical margin and incurved or sinuate laterally, surface simply convex or with shallow and indistinct fovea or impressions, especially towards the base (though with deep impressions in Rhagiosoma) and lateral margins not raised or bordered. Scutellum variable in form but usually proportionally very small. Elytra elongate (1.4-2.5X longer than wide), much wider and longer (2.4-4.4X longer) than the pronotum, and curved or nearly parallel-sided from rounded shoulders to separately rounded or truncate apical margins which often expose part of the pygidium. Surface very variable, smoothly convex or distinctly impressed below the shoulders, randomly and finely to rather strongly punctured throughout or with up to ten variously developed and punctured striae, with or without a scutellary striole, epipleura usually well-developed and complete. Legs always long and robust with the trochanterofemoral junction strongly oblique; sometimes the base of the femora in contact with the coxa. All femora expanded from the base, hind femora often greatly inflated or elongated, especially in males, sometimes with rows of small teeth and/or a large subapical spine. Tibiae usually curved or angled and expanded towards the apex, sometimes with subapical tubercles or teeth but usually without apical spurs. Tarsi 5-segmented; the fourth diminutive and the third strongly bilobed although in males segments 1-3 tend to be bilobed, and often strongly so, on all the legs. While it is true that many genera include rather drab, even superficially uninteresting species, it should be stressed that many species of Sagra - which is generally what the subfamily is known for-are spectacular this can be appreciated from the many images available online.
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Males of many species have greatly enlarged and spurred hind femora and tibiae. This is thought to be from sexual selection but males have not been observed in contests over females and they have not been induced to fight, the exact function, if there is one, therefore remains a mystery although they are used to cling onto foliage and stems while they feed and, to assist in this the legs have numerous tiny hair follicles. Males of many genera are known to be fully-winged but at least some females (Polyoptilus) are brachypterous.