Effects of host grooming on louse populations.

Grooming behaviour by the host is increasingly recognized as an important determinant of feeding behaviour by blood-sucking arthropods. In general, grooming activity increases as a function of attack rate which, in some cases, provides a density-dependent limitation on the success of blood feeding. In turn this can lead to density dependence in population parameters of the arthropod, and can affect transmission of some arthropod-borne parasites in a similar way. But although insect-host interactions at this level are now being revealed in a variety of blood-sucking groups, such as mosquitoes, tsetse flies and triatomine bugs (see Box I), they are perhaps most clearly seen in, populations of ectoporositic insects such as lice, which ore permanently subject to defensive grooming behaviour by their hosts. As Durno Murray discusses here, host grooming has been a dominant factor in the evolution of lice, not only at the morphological level but also in terms of reproductive strategy.