Blister beetles are so called because they are able to secrete cantharadrin, a chemical which can cause skin to blister. There are many species of blister beetle and this one is widespread, although Guernsey is at the northern edge of its range. Presumably, it is a recent arrival as Ivy Bees have only been recorded since 2001. Stenoria analis was first recorded in Jersey in 2009. I need to find out the first recorded sighting for Guernsey and I don’t know if it has been found on any of the other islands.
The beetle is a kleptoparasite: stealing and eating the stash of food that is stored in an undergound cell for the emerging bee larva.How the beetle larvae get from where it hatches to the underground cell is quite remarkable.
The female will lay a clump of around a hundred eggs on plants near to areas where Ivy Bees excavate their nests. The tiny larvae hatch out late August through to September. They have three claws so at this stage they are called triangulins. The photo (taken outside the Bailiwick in our sister island of Jersey – thanks Tim!) shows the larvae with claws facing outwards.
Research from Western France suggests that the traingulins give off a pheromone which mimics that of the female bee (Nicolas J. Vereecken & Gilles Mahe (2007)). Male bees are attracted to the larvae and attempt mating. The triangulins use their claws to attach themselves to the bee’s body. The photo also shows that the body of the larvae do resemble the Ivy Bee.
When the male bee truly mates with a female bee, the larvae cross over to the female who carries her cargo back to the nest. Only one larva has been found in a cell – if there are two, one will kill the other. Presumably the food store is only sufficient for one.
After a few days, the triangulin changes into a grub-like larva which overwinters underground, feeding on the bee egg and its food supply. The adult emerges the following summer.
Stenoria analis was first recorded in Jersey in 2009. I need to find out the first recorded sighting for Guernsey and I don’t know if it has been found on any of the other islands.
Natural history of the Bailiwick of Guernsey 