Host dependency among haematophagous insects: A case study on flea-host association
Obligatory haematophagy is the end result of long standing interspecific associations. Present day specificities to host, blood meal and physiological stage of the host are all offshoots of the primitive interspecific associations. The cause/effect relationship of these dependencies and specificities are probably based on the route through which haematophagy evolved in different groups of insects.
In the present analysis, flea-host association is taken into consideration. It is possible to find an array of host relationships ranging from promiscuous and catholic host associations to strict ones. In general 3 categories may be recognized. In fleas likeXenopsylla cheopis a utilizable protein in an optimum concentration gives the necessary stimuli for maturation (Cheopis-type), while in a second group the stimuli is provided by certain circulating hormones of the host (Cuniculi-type) as seen in rabbit fleaSpitopsyllus cunicuti and in a third grnup (Monositus-type) a priming period characterized by tissue fluid feeding and neosomy is necessary before whole blood diet can stimulate maturation as exemplified byTunga spp.
It appears that vertebrate associations of Siphonaptera initiated as adaptations to the nest microhabitat and haematophagy and adaptations to physical/chemical factors of epidermal habitat being subsequent developments.