Donacia cinerea Herbst, 1784
Suborder:
Superfamily:
Family:
Subfamily:
Genus:
POLYPHAGA Emery, 1886
CHRYSOMELOIDEA Latreille, 1802
Donacia Fabricius, 1775
This is sometimes included in the genus Donaciella Reitter, 1920, a group that includes 6 Palaearctic species; the genus was originally established to include 4 species; D. cinerea, D. microcephala Daniel & Daniel, 1904, D. testaceipes Pic, 1908 and D. tomentosa Ahrens, 1810, all of which have a densely pubescent dorsal surface, but it now also includes the non-pubescent D. clavipes (Fabricius, 1792). It was reduced to a synonym of Donacia by Monros in 1959 but is still widely referred to, especially in the European literature, as a distinct genus or a sub-genus of Donacia. The species has a very wide Palaearctic distribution; from northeast Spain to Tajikistan in the south and extending north to Scandinavia and Siberia. Formerly much more widespread and common in the U.K. it is now local and generally rare throughout England and Wales, very rare in Ireland and there is a single old record from Scotland. The typical habitat is densely vegetated margins of still water bodies e.g. reservoirs, lakes and gravel pits, and the host is usually bulrush, Typha latifolia, or lesser bulrush T. angustifolia, although adults have been recorded on a range of marginal plants e.g. common reed, Phragmites australis, bur-reed, Sparganium erectum and Carex but it is not known whether these act as hosts. Adults occur year-round; the new generation appears from August but generally remain in their cocoons overwinter and become active from March or April, they are usually most abundant from May to August and occur only in small numbers into the autumn. They fly, are easily swept from the host-plants and their presence may be indicated by feeding signs on the leaves; they scrape away the upper epidermis and mesophyll in longitudinal strips parallel to the leaf axis and leave transparent ‘windows’ of lower epidermis. They may be very abundant where found and often occur along with other species, especially the rather more common D. vulgaris Zschach, 1788. The life cycle is spread over three years with overwintering mostly in the adult stage although pupae also overwinter; both feeding larvae and larvae in cocoons have been found in August and larvae are known to feed on the roots of Typha latifolia.
7.5-11mm. Easily identified among the UK Donaciinae by the finely and densely pubescent dorsal surface which gives the species a silky or grey appearance in the field. Elongate with sub-parallel elytra, entirely dull bronze or, occasionally, with a distinct green reflection. Head across the eyes a little wider than the pronotum; vertex strongly convex in the female but rather flat in the male, with a distinct longitudinal impression between convex and prominent eyes, temples with long and distinct pubescence, strongly contracted behind the eyes to a long and parallel neck. Antennae long and slender, proportionally more so in the male, and entirely dark or sometimes with the base of each segment red. Pronotum quadrate to slightly transverse, the surface, except for along the anterior margin, densely punctured and roughly sculptured, anterior margin shiny and bordered, lateral and basal margins without borders, often with a variously developed median longitudinal furrow, and with two large raised lateral tubercles towards each lateral margin which gives a constricted appearance from above. Elytra finely and transversely rugose, with well-developed shoulders and obscure, sometimes absent, oblique depressions in front of and behind the middle, each with ten puncture rows which are not depressed below the level of the flat interstices. Apices obliquely truncate with distinct angles, the inner angle sharp and weakly produced. The legs are robust and entirely pubescent, dark but for the tibial and femoral bases which are to some extent red; the front tibiae sometimes entirely so. The two basal tarsomeres are triangular and evenly broadened to the apices, the third is deeply bilobed, reaching two thirds the length of the last segment, the fourth very small and usually hidden within the lobes of the third. The claws are strongly curved, sharp and lack a basal tooth.