383
Finally, the definition by Eggleton and Gaston (1990) is presented, which is a minor
elaboration of Gauld and Bolton’s (1988) formulation. However, the definition was
borrowed mostly from Kuris (1974).
A parasitoid is an organism which develops on or in another single (“host”) organism,
extracts nourishment from it, and kills it as a direct or indirect result of that development.
These definitions vary in scope, with emphases placed variously on the larval or
adult stages. The more restrictive definition is that of Gauld and Bolton (1988), for
which Eggleton and Gaston (1990) references the deep understanding of
hymenopteran biology by the authors. The less circumscribed definitions of the first
two quotes are not as inclusive and probably exclude clades such as Strepsiptera.
Strepsiptera do not kill their hosts, but rather castrate them, but in any event, a
genetic death is the result. (Consequently, strepsipterans are considered herein as
parasitoids.) More to the point, the first three definitions would exclude organisms
other than insects, an unsound restriction that would disallow mermithinid nematodes (Poinar Jr 2003) and ophiocordycipitacean fungi (Hughes et al. 2011a; Evans
et al. 2011), which clearly are non-insectan parasitoids, often on insects. However,
the last definition of Eggleton and Gaston (1990) would encompass non-insectan
taxa, including the myriad of phyla with parasitoid taxa in the marine realm
(Weinstein and Kuris 2016). Because the definitions of trophic groups such as herbivore, parasite and predator are functional descriptions, the simple, functional definition immediately above by Eggleton and Gaston (1990) is proposed for a
parasitoid, with minor exceptions, based on an earlier meaning by Kuris (1974).
Such an ecumenical definition would include mermithid nematodes and ophiocordycipitacean fungi mentioned above and probably hemiepiphytic plants that ultimately kill their host plants (Putz and Holbrook 1989).
11.2.5 Types of Parasitoidism
Parasitoidism represents a complex interplay of ecological and behavioral phenomena. These phenomena can be categorized in many ways, some of which are binary
contrasts and others that are terms for singular, distinctive types of parasitoidism.
The major types of parasitoid relationships in common usage are detailed below.
11.2.5.1 Ectoparasitoidism Versus Endoparasitoidism
Parasitoids that develop within the body and feed on the internal tissues of their host
are endoparasitoids. Ectoparasitoids, by contrast, live on the external surface of
their host although often their mouthparts are buried into deeper subcutaneous tissues. Complexities to these two contrasting definitions are parasitoids which include
species that spend part of their development as endoparasitoids and the other part as
ectoparasitoids (Godfray 1994), or parasitoids that have their bodies partly located
deep in host internal tissue and partly exposed to the surface (Cook 2014).
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution
Finally, the definition by Eggleton and Gaston (1990) is presented, which is a minor
elaboration of Gauld and Bolton’s (1988) formulation. However, the definition was
borrowed mostly from Kuris (1974).
A parasitoid is an organism which develops on or in another single (“host”) organism,
extracts nourishment from it, and kills it as a direct or indirect result of that development.
These definitions vary in scope, with emphases placed variously on the larval or
adult stages. The more restrictive definition is that of Gauld and Bolton (1988), for
which Eggleton and Gaston (1990) references the deep understanding of
hymenopteran biology by the authors. The less circumscribed definitions of the first
two quotes are not as inclusive and probably exclude clades such as Strepsiptera.
Strepsiptera do not kill their hosts, but rather castrate them, but in any event, a
genetic death is the result. (Consequently, strepsipterans are considered herein as
parasitoids.) More to the point, the first three definitions would exclude organisms
other than insects, an unsound restriction that would disallow mermithinid nematodes (Poinar Jr 2003) and ophiocordycipitacean fungi (Hughes et al. 2011a; Evans
et al. 2011), which clearly are non-insectan parasitoids, often on insects. However,
the last definition of Eggleton and Gaston (1990) would encompass non-insectan
taxa, including the myriad of phyla with parasitoid taxa in the marine realm
(Weinstein and Kuris 2016). Because the definitions of trophic groups such as herbivore, parasite and predator are functional descriptions, the simple, functional definition immediately above by Eggleton and Gaston (1990) is proposed for a
parasitoid, with minor exceptions, based on an earlier meaning by Kuris (1974).
Such an ecumenical definition would include mermithid nematodes and ophiocordycipitacean fungi mentioned above and probably hemiepiphytic plants that ultimately kill their host plants (Putz and Holbrook 1989).
11.2.5 Types of Parasitoidism
Parasitoidism represents a complex interplay of ecological and behavioral phenomena. These phenomena can be categorized in many ways, some of which are binary
contrasts and others that are terms for singular, distinctive types of parasitoidism.
The major types of parasitoid relationships in common usage are detailed below.
11.2.5.1 Ectoparasitoidism Versus Endoparasitoidism
Parasitoids that develop within the body and feed on the internal tissues of their host
are endoparasitoids. Ectoparasitoids, by contrast, live on the external surface of
their host although often their mouthparts are buried into deeper subcutaneous tissues. Complexities to these two contrasting definitions are parasitoids which include
species that spend part of their development as endoparasitoids and the other part as
ectoparasitoids (Godfray 1994), or parasitoids that have their bodies partly located
deep in host internal tissue and partly exposed to the surface (Cook 2014).
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution