The warm weather in May and June did produce a large emergence of our local comb-horned craneflies Dictenidia bimaculata and Ctenophora pectinicornis. In most years I get one or two records of these species at best but this Spring I had records from new sites and a very large emergence at Yardley Chase. They have the common name "comb-horned" as the males have antennae which bear two rows of branches, like the teeth of combs. The cranefly larvae live in rotting wood in mature trees, often high up in branches. The adults are occasionally seen near the ground after emergence. The comb-horned antennae are thought to be an adaptation to allow the males to find females by detecting their pheromones. In the tree canopy sensitive detectors would be needed to find a mate.
The reason for the sudden increase in records is probably down to the tendency for these insects to emerge in warm conditions.
Dictenidia bimaculata male showing the "comb-horned" antennae
Ctenophora pectinicornis female. This mimics a wasp but the projecting spike at the end of the abdomen is harmless. It is the ovipositor for laying eggs.
Neither species is very common. They are best looked for near ancient trees with rotten branches in woods or parks on warm days in late May and June. They often rest on tree trunks or nearby vegetation. Photos of them with details of location and date would help us find more sites for them. There are a few other comb-horned craneflies in Britain, some are extremely rare, so do try to photograph any you may come across. Photos can be posted on the Facebook WILDside Project Group.
