> Parasites and their hosts show behavioral as well as physiological interactions. Parasites are able to alter the behavior of their hosts, and hosts in turn may employ behavioral retaliation in response to parasitic infection.

> Host suicide is the term coined to describe aberrant behavior on the part of an infected host which leads to increased probability of death by predation. Host suicide will increase the inclusive fitness of the host if (1) the suicide prevents the maturation of the parasite; (2) the mature parasite is more likely to infect the host's kin than nonkin; and (3) the benefit to the host, in terms of the increased fitness of the kin, is greater than the cost of the suicide, measured in terms of the loss of the host's own reproductive fitness.

> Host suicide is most profitable when the host is infected by a parasitoid. The parasitoid reduces the host's reproductive fitness to zero, so that the cost of the suicide is also zero.

FROM:

Smith Trail, D.R. 1980. Behavioral Interactions Between Parasites and
Hosts: Host Suicide and the Evolution of Complex Life Cycles. The
American Naturalist 116(1): 77-91.

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