The defensive glands of beetles, Tenebrio molitor,
infected with metacestodes (cysticercoids) of Hymenolepis diminuta are
everted less frequently upon stimulation, and contain less toluquinone
(methylbenzoquinone) and m-cresol, than glands
of uninfected controls. These differences, as shown in predation trials
with wild rats, increase the likelihood that both
cysticercoids and beetles will be ingested by the tapeworm's definitive
host. This is the first documented case of a parasite
inhibiting the chemical defence of an intermediate host, and one of only
a few reports of parasite-induced manipulation
of host biology supported by empirical evidence implicating
facilitated parasite transmission between host species.