|Helophorus brevipalpis Bedel, 1881|
|Generally common and often abundant throughout England, Wales and Scotland
with the exception of the Grampians and the Highlands although there are modern records from the far north coast.
Occurs on all our islands including Scilly, Lundy, Hebrides, Orkney and Shetland (NBN). The species is common throughout our Watford
area, invariably so around wetland habitats but we have often found them far from water, both diurnally by general sweeping, and
nocturnally when they may may be attracted to light in many situations. During May 2007 we found them in numbers during hot
sunshine on cars parked near to the river Colne at Radlett road. Typically a species of stagnant water
environments; small ponds rich in vegetation or temporary grassy pools but also beside slower stretches of
running water (Hansen), the adults inhabit marginal
soil and roots etc and are vegetarian, feeding on filamentous algae and decomposing vegetation. They are active
from early spring through to the autumn, overwintered adults become active from March onwards and may occasionally
be swept in flight around suitable habitats. New generation adults emerge later, from the middle of June and fly readily
in order to colonise new areas. The reproductive organs of newly emerged adults are small and remain so for three of four months, maturing
in October or November when mating begins. These may be active in the winter and produce eggs at this time but the majority
begin breeding in the spring. Eggs are laid within a silken cocoon constructed by the adult on marginal silt or
among vegetation, in brevipalpis this consists of an egg chamber with, at one end, a flat, concave and
leaf-like 'mast' which may act as a plastum during temporary flooding (photographs of egg cocoons are given by Angus,
1974). Larvae hatch within a week or so and are terrestrial, living on marginal soil, and carniverous. This stage is
rapid; they feed for about two weeks during which time they moult twice and then burrow into soft soil to pupate.
Adults emerge after two weeks but may remain in the soil, possibly waiting for floodwater.
1.9-3.5mm (friday). Appearance varies due to the extent of dark markings on the elytra. Head black and strongly metallic; purple, bronze or green, often in combination. Granulate (this varies in strength) and finely punctate to front margin. Eyes strongly protruding and excised on hind margin. Stem of Y-groove very obviously widened from base. Palps brown, generally darkened towards apex, apical segment varies in proportion and may be short or long oval but is always symmetrical although the specimen may need to be manipulated to appreciate this. Antennae 9 segmented, brown with club darker. Pronotum black, metallic as head, with anterior and ;ateral margins pale brown. Transverse, broadest in front of middle and evenly curved or almost straight to obtuse hind angles, this varies as sometimes the sides are weakly sinuate before the hind angles and we have a couple of 'odd' specimens in which the lateral margin is almost straight from front to hind angles - these were found among a large (200 plus) sample examined from Cassiobury park. Lateral margins bordered and finely crenulate. Surface granulate, variable in strength. Elytral shape varies; widest at or near middle with sides smoothly rounded to apex. Each elytron with ten complete rows of well impressed punctures, these become smaller towards the apex, without an abbreviated basal stria. Interstices weakly convex and finely puntured. Usually with a series of dark markings; an inverted V shaped sutural mark behind middle, in some specimens this may be the only dark mark, a dark mark towards the apex across striae 3-5 and another at, or behind, the middle across striae 6-8. Elytral flanks as wide as, or nearly as wide as, epipleurs at the level of the metacoxae. Legs pale brown with apical tarsal segment(s) darker. Tibiae with rows of fine spines and several well developed apical spurs. Tarsi 5-5-5 although the basal segment is tiny so they appear 4-4-4, upper surface with fine swimming hairs but these are very different to see with the light microscope. Claws well developed, smooth and with a small basal tooth.
The aedeagus provides characters which will help determination, or may even be essential, of Helophorus species. H.brevipalpis is distinguished by the more or less straight lateral pronotal edges, broadly visible elytral flanks, lack of abbreviated elytral striae and symmetrical terminal segment of the maxillary palps. In a large sample the general shape, markings, form of pronotum and proportions of palps will be seen to vary but with experience this species becomes obvious. (We hope to feature the aedeagus in due course).
Description from 19 Watford specimens at X40