Cantharis thoracica (Olivier, 1790)

Quoted in Joy as very local; England and southern Scotland. Although there are modern records throughout England and Wales this is a very local insect which, no doubt restricted by its habitat requirements, is absent from many areas eg much of south Devon, Essex, Kent, Lancashire, Yorkshire, north Wales and most of Hertfordshire and Buckinghamshire (Alexander). Usual habitat is marginal vegetation, reedbeds, fens and marshes, the adults occurring between June and August. Our local records are restricted to a few specimens swept from vegetation around disused watercress beds below Cassiobury park (July 07) although there are records from further south, towards Rickmansworth (Trevor James Pers. Com).

The small size and parallel form, shiny black elytra and red scutellum will identify the species in the field.

4.5-7mm. Head black from base to front margin of eyes, front of head and mouthparts testaceous. Surface shiny, finely punctate and pubescent. Eyes convex and prominent, temples curved and contracted to base. Clypeus convex between antennal insertions. Terminal segment of maxillary palps broadly triangular. Antennal segments elongate, segment 2 shorter than others, basal segments testaceous, distal segments dark. Pronotum entirely testaceous, very finely punctured and pubescent without microsculpture (X20) Transverse (7:5), convex with margins explanate, front angles rounded, hind angles obtuse and hind margin sinuate. Scutellum testaceous or with edges darkened, finely punctate and pubescent. Elytra shiny black, epipleurs beneath shoulders testaceous, this may be obscure or may be clear and extend to entire epipleur ie as far as the beginning of the lateral sinuation. Surface strongly granulate, pubescence semi-erect, sparse and long. Apex weakly rounded, almost truncate, covering hindwings and (usually) abdomen. Legs testaceous but for darkened apical tarsal segments. Third tarsal segment bilobed, fourth much more deeply and strongly so. Claws appendiculate.

In var. suturalis Schil. there is a yellow area around the elytral suture, especially towards the scutellum (Joy).

Description from 2 Watford specimens at X20