Crioceris asparagi (Linnaeus, 1758)
This widespread Palaearctic species occurs from Spain westward through Asia Minor to Turkmenistan and western Russia, north to Scandinavia and south to Algeria and Tunisia including the Mediterranean Islands and Madeira, and is now widespread in North America and Canada following introductions. In the U.K. it is locally common in central Southern England, becoming less so in the midlands and the west. They may be found on the food plant, Asparagus officianalis, both the wild type and its garden and commercial varieties, in a wide range of habitats; heathland, dunes, parkland and gardens etc. and they may become a pest where the plants are grown commercially. The adults fly and may be found year-round; during the winter near the host, among litter, in old stems or nearby under bark etc. and they become active early in the year, during March or April when they commence feeding on young leaves and stems of emerging plants. Oviposition occurs during June and July when the eggs are attached to the stems in short rows of 3-8, they are easily seen and distinctive; grey or brown, elongate and relatively large in relation to the adult beetle. The larvae hatch after a week or so and feed on the foliage, they pass through 4 instars and are fully developed within a month. They are generally obvious among the foliage; dull grey with a black head and rather short and fat, and they will usually be present alongside the adults, when disturbed they exude a fluid and may drop to the soil. When fully grown they descend the stems and burrow a few centimetres into the soil where they construct a silken pupal chamber, the pupal stage lasts for 2 or 3 weeks and new generation adults appear during July and August. These adults will feed for a few days before mating and laying eggs which will produce a further generation of adults during September and October. These adults will feed for a while before overwintering. The number of generations varies; typically there are 2 in central Europe and the U.K. but there may sometimes be only one, and in the U.S.A. there may be up to 4.
In the U.K. this species varies little and is quite distinctive among the fauna. 5-6.5mm. The colouration will serve to identify the species; head metallic dark blue or black, pronotum red or orange often with a dark discal mark. The elytra are dark metallic with 4, including the apical, pale marks. Appendages dark, generally with the tibiae pale towards the base. The sexes are superficially similar but in the male the pro-tibiae are more strongly curved.
On the continent the species is variable with the elytra ranging from completely dark to completely pale with a dark suture and 3 dark spots on each, replacing the transverse markings seen in the typical form. Two subspecies are recognized; the central Asian subspecies C.a.turkestanica Medvedev, 1955 has a strongly punctured pronotum while in C.a.maculipes (Gebler, 1834) the femora and tibiae are at least partly pale. A range of intermediates have been recorded.
The widespread continental species C. duodecimpunctata (Linnaeus, 1758), (The 12-spotted Asparagus Beetle), has also been recorded in the U.K. but has never become established. It is a very striking species; bright red or orange with 6 black spots on each elytron.
CRIOCERIS Geoffroy, 1762
This is a small genus of about 20 species which are diverse and widespread in tropical regions but rather less so at higher latitudes; 9 species occur in the Palaearctic region and only 2 in the Nearctic, one of which is introduced from Europe. C. nigropicta Wollaston, 1864 is a Canary Island endemic. Host plants are restricted to the Asparagaceae and several species are pests of commercially grown crops, more especially so as the adult beetles are active early in the growing season when damage may be more severe, they are generally ‘controlled’ by pesticides.
They are medium sized beetles, 5-8mm, characterized by distinctive dorsal patterns of dark or dark metallic markings on a pale ground colour. The head and pronotum are narrower than the parallel-sided elytra and the dorsal surface is glabrous or nearly so. The head is as wide as the pronotum with large and prominent eyes that are variously emarginate, the clypeus is large and triangular and distinctly separated from the broad frons. Mandibles robust and toothed at the apex. Antennae filiform. The pronotum is cylindrical and quadrate, or nearly so, without lateral borders and constricted near the base; sometimes only very weakly so. Scutellum small. Elytra with punctured striae and rounded apices which completely cover the abdomen. The legs are robust, the tibiae without, or with only tiny apical spines. The third tarsal segment is deeply bilobed and the claws are free. The variation in colour in some species has lead to a number of named colour varieties. A single species occurs in the U.K.