The common hen flea
Ceratophyllus gallinae is a species of flea that feeds on many different birds, as well as a few mammals. In Europe, however, the vast majority of its hosts are hole-nesting tits, particularly great tits and blue tits.
I worked with C. gallinae at the University of Bern, Switzerland from 1994 to 1997, looking for effects of variation in host quality and nutritional status on flea fitness.
|The drawing above shows an adult female Ceratophyllus gallinae laying an egg. In order to do start laying eggs, she needs to feed on the host several times. Unlike mammal fleas, which often remain on the host and feed for long periods, hen fleas spend most of their time among the material of the host's nest, and only hop on to the birds to feed for short periods. |
The eggs laid by the female hatch into long, thin larvae, shown in the lower part of the drawing above. These feed on detritus amongst the nest material and on undigested blood which the adult fleas pass in their faeces. The larvae develop in a few weeks, and pupate inside a silk cocoon. Then they emerge as adults, mate and continue the cycle.
Reproduction can only take place when there are birds to feed on in the nest, so at the end of the host's breeding period those flea larvae that are left in the nest will spin their cocoons for pupation, and then remain in these throughout the summer, autumn and winter, as either larvae or pupae. If the nest is reused by birds the following year, then the pupae will hatch and the adults will mate, feed on the new hosts, and continue the cycle.
However, if the nest is not reused, the adults cannot feed and reproduce - then they will often hatch and make their way to the nest entrance (see right), where they may be able to disperse to a new nest, often by jumping onto a bird that is examining the old nest as a potential nest site.
Hen fleas clustering around the entrance to an unused nest box in Bern, Switzerland