Parasites, host odors

Ectoparasites such as ticks, mites and haematophagous flies together with certain endoparasites may be "managed" by use of avermectins (macrocyclic lactones) or hormone analogues and by Immunization of the hosts with antigens derived from the vectors or parasites themselves. Recently this combined approach has been used most effectively against helminth infestations as well as against ticks and flies. Use of components of host odors and pheromones to trap, sterilize or kill tsetse flies is described as well as inexpensive methods of crop and livestock protection, such as oils and plant extracts, used traditionally in less developed countries. 

During August, the host queen typically abandons her nest, but the parasite stays on. By the end of August, a new generation of parasites emerges and the parasitic queen has no further need for her disguise. Her alkenes reappear, and with them she resumes her own unique odor. How she turns the synthesis of alkenes off and on is still a mystery. 

Turlings TCJ, Tumlinson JH, Lewis WJ (1990) Exploitation of herbivore-induced plant odors by host-seeking parasitic wasps. Science 250 1251-1253... 

Beta-glucosidase an elicitor of herbivore-induced plant odor that attracts host-searching parasitic wasps. Proceedings of the National Academy of Sciences, USA 92 2036-2040. 

Pamilo, 1996 although template and acceptance thresholds adjust with time, see D Ettorre et al., 2004a Brandt et al., 2005 Errard et al., 2006a). Enslaved host workers eclose in parasite colonies, and thus their template resembles the parasite odor, a condition which may let them accept parasites. Indeed, P. breviceps immature stages (eggs and pupae) possess distinct hydrocarbon profiles from their host species, but are cared for by Formica workers (Johnson et al., 2005) and, similarly, pupal hydrocarbons of Harpagoxenus sublaevis do not depend on their host species (Kaib et al., 1993). 

In the free-living Polistes nimphus wasps, behavioral bioassays on manipulated colonies have documented that queens that behave as social parasites and usurp conspecific colonies effectively mimic the host-nest odor and become accepted by resident workers (Lorenzi et al., 2007). The process of concealing identity to host residents by P. nimphus usurpers occurs in only 4 days and might involve the absorption of chemicals from the host... 

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