Cryptorhynchus lapathi (Linnaeus, 1758)

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POLYPHAGA Emery, 1886

CURCULIONOIDEA Latreille, 1802

CURCULIONIDAE Latreille, 1802

CRYPTORHYNCHINAE Schönherr, 1825

CRYPTORHYNCHINI Schönherr, 1825 

CRYPTORHYNCHINA Schönherr, 1825

CRYPTORHYNCHUS Illiger, 1807

This Holarctic species is generally common throughout Europe from the northern Mediterranean coasts to the UK and the north of Scandinavia, it occurs throughout the central and northern Palaearctic region, including Japan, and is widespread in North America. Here it occurs throughout England, Wales and southern Scotland, it may be locally common in East Anglia and around coastal areas of south and north Wales but is otherwise very local, sporadic and generally scarce. Typical habitats are wetland margins and damp woodland and fenland where the host plants are common in various stages of growth, these are generally a wide variety of willows, osiers and poplars but various other trees such as alder and birch have been recorded. Throughout its continental and American distribution it is sometimes a serious pest of intensively grown willows and can be commercially damaging, it was formerly a minor pest in the UK when basket-weaving was more popular but it is now at most a nuisance. Adults occur year-round but are mostly recorded from May until July, the life-cycle is very adaptable but they generally overwinter either among decayed wood and bark or in leaf litter or soil at the base of trunks etc. or fully-formed within the pupa, and become active from April, then after a brief period of feeding on soft and tender bark they mate early in the season and females oviposit during May and June. Eggs are laid singly or more rarely in small numbers in tiny holes or slits chewed into the bark on branches or small trunks and larvae emerge after a week or two, they initially feed within the cambium but as they grow they also tunnel into the xylem, producing straight or erratically-winding galleries as they feed and sometimes inducing the formation of galls around leaf nodes, they may develop through the summer and autumn and then overwinter in the wood to complete their development in the spring, or those from early eggs may pupate in late summer and produce adults from August, some of which become active and even mate and lay eggs which will overwinter, and some that will remain within the pupa until the spring. Pupation occurs in the feeding gallery and this stage lasts about two weeks.  In the UK the life-cycle usually takes two years but in Canada and northern continental areas it may take three. Adults rarely occur in numbers, they are both nocturnal and diurnal and spend most of their time in bark crevices or exposed on small stems where they strongly resemble bird droppings and so will need to be searched for very carefully.

Adults are large, 5.0-8.7mm, and very distinctive among our fauna due to the overall shape, bicoloured elytra, and tibial apices which are produced into a sharp internal tooth-like process. Head and rostrum dark with scattered pale scales, pronotum typically dark with a small patch of pale scales on each lateral margin, two more along the base and several tufts of raised dark scales on the disc, basal two-thirds of the elytra extensively dark with a variable oblique pale stripe from the shoulder to the suture, apical third abruptly pale, interstice 3, 5 and 7 with small patches of raised scales. Head almost circular, with curved temples and weakly convex eyes continuous with the outline, rostrum weakly dilated at the base; longer, shinier and less strongly punctured in the female. Pronotum transverse and evenly curved laterally, weakly constricted before rounded anterior angles and with obtuse posterior angles, basal margin produced medially. Scutellum small, transverse and rounded. Elytra much broader across the base than the pronotum, with prominent shoulders and almost parallel in the basal two thirds, rather abruptly narrowed and weakly sinuate to a continuously-rounded apical margin.

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