When I was wandering around my garden one evening I noticed a European honeybee hanging strangely from a flower. On closer inspection I saw a well-camouflaged spider holding the bee in place and a number of small flies covering its body (see photo). I can understand the spider鈥檚 role in all this, but what are the flies doing?
鈥� A honeybee will typically visit up to 500 flowers on each nectar-foraging trip. Foraging bees store nectar in a swollen region in the oesophagus called the crop or honey stomach, which can swell with nectar to fill a major proportion of the insect鈥檚 abdomen.
As the crop fills with nectar, enzymes act on the complex sugars it contains, breaking them down to simpler sugars. On returning to the hive, the bee will regurgitate the contents of its crop for other bees to concentrate and further metabolise, ultimately making honey.
Advertisement
鈥淥n return to the hive the bee will regurgitate the contents of its honey crop so others can make honey鈥�
The bee the questioner saw has been ambushed by the spider. During the struggle with the spider, or as a result of muscular contractions in response to the spider鈥檚 venom, the bee鈥檚 crop has ejected its payload, which has seeped over its body.
It is probably the sweet scent of the partially metabolised nectar that has attracted the flies: the ones in the photograph look like fruit flies of the Tephritidae family. The mouthparts of flies like these are unlikely to allow them to drink nectar directly from the lilly-pilly flowers, but they can still take advantage of this impromptu sugary meal.
The spider has probably had to stay with the bee for some time to make sure it is immobilised, giving the flies time to congregate on its body. The flies are too small to be of interest to the spider, so they are in no danger.
Peter Scott, Hove, East Sussex, UK