COLEOPTERA > POLYPHAGA > STAPHYLINOIDEA > Silphidae

Silphids are medium to relatively large-sized beetles that are typically associated with carrion or decaying organic matter on which they both feed and reproduce, although a few species are specialist predators of snails or caterpillars, and a couple feed on living vegetation.

There are two subfamilies, Silphinae and Nicrophinae, with the former being represented in Britain by 14 generally dark-coloured beetles that have an oval, somewhat flattened shape. There are two though that stand out from the rest of the pack. Firstly, Dendroxena quadrimaculata, the arboreal predator of moth caterpillars, which is one of the smaller species at 10-14mm. This rather attractive beetle is primarily orangey-brown with a black head, pronotal disc and scutulum, and with two black spots on each elytron. Unfortunately, it's a scarce species with no reported sightings from Dorset.

The other is the unmistakable Red Carrion Beetle, Oiceoptoma thoracicum, which is far more widespread, although not particularly common. They grow to 16mm and are entirely dark grey to black apart from their orangey-red pronotum. Adults are generally active from April to September. They are associated with a range of decaying organic matter, but will more likely be found on the carcasses of small animals or birds. Interestingly, as with many of these species, they have an incredible sense in detecting fresh carrion and will quickly fly over long distances to colonise it.

Of the remaining species, Phosphaga atrata is by far the most frequently recorded. It's generally known as the Black Carrion Beetle, which is rather strange given that there are a few other uniformly black species and also because it has an almost completely red form. The normal form though is entirely black and distinctive with a small head, well-rounded pronotum, and elytra with longitudinal ridges. The whole of the upper surface of the body is punctured, particularly strongly and densely on the elytra. They range from about 10mm up to 15mm in size. The adults do not fly so can only disperse and colonise new areas by walking unless transported by other means such as on timber. They occur primarily in damp deciduous woodland, but also in other habitats including gardens and damp grasslands. During the winter months they can often be found under bark and deadwood and even in the warmer summer months you'll rarely find them in the open during the day. They typically hold their head under the thorax when at rest and if disturbed secrete a foul-smelling yellow liquid to deter any would-be predator. They mainly feed on earthworms and certain types of snails, which they attack with a salivary secretion that breaks down the snail's tissue allowing the beetle to gain entry to the shell.  ​

Far less common is the fairly large, although quite variably sized, 10-18mm long, dull black species Ablattaria laevigata, which has a finely and densely punctured head and pronotum, and pitted, but relatively smooth elytra. A quick look at the records on the NBN Atlas database show that it is pretty much restricted to southern Britain, south of the Wash. Locally there haven't been that many confirmed sightings in recent years; just ten from Dorset (VC9) and only four from South Hampshire (VC11). The individual I found at Martin Down was in typical habitat for this particular species as most inland records are from grassland or open scrubby areas on chalk or sandy soils. Further west, it seems to occur more frequently in coastal locations.

The second group are the beetles of the genus Nicrophorus, commonly referred to as Sexton Beetles, which are well known for their habit of burying small vertebrate carcasses. They are reasonably large chunky beetles with big eyes, clubbed antennae and truncated elytra.

Although 7 species have been recorded in Britain, one is presumed extinct and another is very rare. I'm not sure how true it is, but I read that you're more likely to encounter one of these Sexton Beetles than any of the members of the Silphinae subfamily, which is good to know even though I'm still looking! The distribution maps show that four can be found locally. Nicrophorus humator is the largest at 18-26mm and the only extant member of the genus with entirely black elytra. Nicrophorus interruptus, N.vespillo and N.vespilloides average smaller, but are variable in size. These species have  attractive black and orangey-red, or dark red in the case of N.vespilloides, banded elytra; as does the remaining species N.investigator which, despite being common and widespread, has not yet been officially recorded from Dorset.

Updated, Jan.25 (v.3)