There is just a single British species of drilid, Drilus flavescens. It is a Nationally Scarce (Na) species mostly found on the chalk downs of south-east England where it preys on snails. Adult males and adult females are very different – the males can fly and have strongly pectinate antennae which probably help them to locate the females, which by contrast are large, wingless and grub-like. Males are relatively easy to see in the right habitat from about mid-May to early July, often active in the grassland ‘canopy’. By contrast, seeing a female Drilus seems to be a once-in-a-lifetime experience, and I haven’t had my one yet. In April 2012, I couldn’t even find a photo of a female Drilus on the internet! But in June 2012, Dave Gibbs sent me these photos of an adult female Drilus flavescens which he reared from a larva.
To illustrate just how bizarrely different the males and females are, here’s a mating pair:
A few years ago, Graeme Lyons sent me a photo of an extraordinary beetle larva. I eventually worked out it was a Drilus larva and since then I’ve seen quite a few photos either sent to me or posted on iSpot. They are extremely striking and highly distinctive, and clearly quite active in daytime, searching for snails to prey on. Here’s a selection of larval pictures, mostly assembled by Penny Green from Sussex naturalists: thanks to Penny, Kate Frankland, Richard Roebuck and Tim Wilton.
Lionel Crawshay (1903) published a paper on the life-history of Drilus flavescens describing three years of observations on this species. It’s full of excellent information but inevitably does not answer every question, and I still don’t know whether these peculiar holes in snail shells could have been made by Drilus or not.
Drilus is mapped in Keith Alexander’s (2003) Provisional atlas of the Cantharoidea and Buprestoidea (Coleoptera) of Britain and Ireland, published by the Biological Records Centre (see their website), and is included in the Soldier Beetles, Jewel Beetles and Glow-Worms Recording Scheme run by Keith Alexander who would be pleased to receive records and happy to help with any identification problems: contact details here.
Crawshay, L. (1903). On the life history of Drilus flavescens, Rossi. Transactions of the Entomological Society of London, 51, 39 – 51 and plates I and II.