One of the groups of flies that I love watching are the robberflies. They are quite ‘lazy’ in flight and frequently stop where you can take a good look at them, especially if they have just caught something and are stopping to feed. 

They are called robberflies because they are very efficient hunters of small flying insects, mainly other flies but also wasps and beetles. Robber seems a bit harsh as they are doing a good job of controlling other insect populations, an honest job.

They are mainly restricted to ‘good’ habitats and so may be good indicators of the health of a habitat, so I prefer to think of them as the good guys, cops rather than robbers. 

There are 29 species of robberfly in the UK. The smallest are only about 1cm long, the slender and slender-striped robberflies that hunt in open grasslands.

The largest is the UK’s largest fly the hornet robberfly that reaches almost 3cm. This one is still quite scarce but is found on several BBOWT reserves which are managed by grazing, including Yoesden and Dancersend.

Most of the species lay eggs in dead plant material including wood and cow dung, and it is thought the larvae, like the adults, are predatory helping control other insect numbers. Depending on species the robberfly life cycle may take one to three years. 

I have seen at least 15 of the 16 species recorded so far in the BBOWT region and may be able to find a few more if I am lucky, but the ones you are most likely to see are

• the common red legged robberfly, which skulks along woodland edges,
• the slender-footed robberfly, which loves grassland or,
• most common of all on chalk grassland, the kite-tailed robberfly, an odd name, so called for a small projection under the end of the males abdomen, watch out for it sunning itself on fence posts in mid to late summer.

We have three quite rare species in the BBOWT area:

• the downland robberfly that is restricted to really good quality chalk grassland,
• the elusive false slender-footed robberfly of which there are seldom more than two UK sightings a year, and
• the lovely golden-haired robberfly that is restricted to ancient oak woodlands such as Whitecross Green Wood.

How to recognise a robberfly? Large eyes either side of antennae that form a Y shape. They have a long body and quite long legs, the front pair have spines / stiff hairs that help the fly to capture its prey.  

If you want to know more then there are some excellent resources on the Soldierflies and Allies Recording scheme website and, as always, all records are welcome! Please add your records to iRecord or send direct to the Soldierflies and Allies Recording scheme.

Sue Taylor
(Volunteer recorder for BBOWT, focusing on entomology)

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