Carabus violaceus Linnaeus, 1758
Violet Ground Beetle
This widespread and generally common species occurs throughout the Palaearctic region to the north of Scandinavia and from Portugal to the far east of Asia and Japan; at least 10 subspecies are recognized of which 2 occur in the U.K. Here it occurs throughout mainland U.K., Anglesey and the Western Isles but not Ireland, the Isle of Wight, Orkney or Shetland and records are very sparse from the West Country. The usual, widespread subspecies is C. v. solicitans Hartert, 1907, and ssp. purpurascens Fabricius, 1787 occurs only along the south coast. This is our most common Carabus, occurring in a wide range of not too wet habitats; it is most often encountered in wooded situations but also occurs in parkland, gardens, moorland and overgrown grassland etc. and may also occur in urban areas e.g. we have found them in numbers around communal refuse bins below high-rise flats in South Hertfordshire. Adults occur throughout the year and are nocturnal, spending the day under logs and bark etc. or in the soil, they are flightless, become active at dusk and may cover a wide area as they move rapidly in search of prey. Both adults and larvae are predatory, consuming mostly soft-bodied prey such as slugs, snails, worms and insect larvae but will take a wide range of food as necessary. In the U.K. breeding occurs in the autumn whereas further south they are summer breeders, eggs are laid singly or in small groups in the soil or among accumulated organic debris, and larvae emerge after a week or two, they feed and develop through the winter, passing through several instars, and pupate during the spring in a cell in the soil or under logs or bark etc. adults eclose after about 3 weeks and new generation beetles occur from April or May. Adults may be long-lived and overwinter after breeding, they are active and continue feeding in all but the coldest weather when they will remain inactive under logs or in the soil until the temperature increases. During the warmest summer months they may also aestivate in the soil until conditions improve. Adults have been kept as pets and successfully bred in captivity; larvae have been kept isolated in large containers containing soil and leaf litter and maintained at 50% R.H, and 19oC, and fed on Zophobus larvae and isopods, mostly Philoscia muscorum (Scopoli, 1763) and Oniscus asellus Linnaeus, 1758. Development to pupation takes about 10 months, pupation occurs in the soil and adults appear in the spring.
At 20-30mm and with its distinct colouration this species could only be confused with the closely-similar C. problematicus Herbst, 1786 (see below). Entirely dull or silky black with metallic violet, blue or greenish margins to the pronotum and elytra. Head quadrate with prominent mandibles and eyes, vertex and frons rugose and labrum gently incurved anteriorly. Palps long and prominent with the apical segment expanded and truncate apically, penultimate segment of the labial palps with more than 2 setae along the inner margin. Antennae entirely dark. Pronotum transverse with rounded anterior angles, backwardly-produced posterior angles and distinct lateral and basal borders. Surface rusose. Elytra long and evenly curved laterally to continuously rounded apices, suture fused, with a narrow and metallic explanate margin. Surface rugose, sometimes with the sculpture more defined and tending to run in longitudinal lines, in purpurascens the elytra are more elongate and heavily sculptured, basal margin without a border. Legs entirely dark metallic, anterior tibiae smooth along the inner margin i.e. without an antenna-cleaning notch, and all tibiae with 2 strong spurs on the inner apical angle. Males are distinct in having the basal pro-tarsomeres dilated.
Fig. a) Pronotal convexity in C. problematicus (left) and C. violaceus (right).