499
Feener and Brown 1997). These data may indicate that for parasitoids, host breadth
of intermediate selectivity would be favored (Ferns and Jervis 2016), generating
specialists and generalists on opposite sides of the host specificity continuum.
11.9 Summary and Conclusions
Many extant and extinct insects are predators, parasites or parasitoids. However,
explicit recognition of parasitoidism as a distinct ecological process on par with
predation and parasitism has been a relatively recent development. Parasitoidism
historically was categorized by its location on the host (ectoparasitoidism versus
endoparasitoidism), by presence on the same host individual of multiple conspecifics (superparasitoidism) or by multiple non-conspecifics (multiparasitoidism).
Other descriptive designations common in the parasitoid literature are hyperparasitoidism, the condition of parasitoids living on other parasitoids, and cleptoparasitoidism, the killing of a host individual resulting from a parasitoid absconding food
or other vital resources. Direct and indirect evidence for predation, parasitism and
parasitoidism in the fossil record consists of biomolecular data, taxonomic affiliations, morphological and functional attributes, gut contents and coprolites of body
fossils, in addition to host-tissue damage, plant–insect interactions and sedimentary
structures of trace fossils. Parasite and parasitoid insect clades overwhelmingly
have targeted 84 clades of holometabolous insects and minimally targeted 4 clades
of hemimetabolous insects. The accumulation curve of originations for parasitoid
larval dietary substrates through geologic time records a major upward trend, in
contrast to more gently increasing trends for fungivory, phytophagy and predation.
Contrary to parasitoid evolutionary trajectories, the larval dietary trajectory for
ectoparasites resulted in evolutionary cul-de-sacs that did not lead to major diversification events. Parasitoids from three orders of insects—beetles (Coleoptera), flies
(Diptera) and wasps (Hymenoptera)—document the multiple and complex paths
that various lineages transit into and out of the parasitoid life habit.
Parasites and parasitoids have fossil records ranging from poor to fair, although
their modern diversities can be very elevated. Ten groups of parasites occur among
hemimetabolous and holometabolous insects. Hemimetabolous parasites are cockroaches (Blattodea) consisting of an extinct fossil lineage; earwigs (Dermaptera),
with two lineages parasitic on bats and rodents; bark lice (Psocoptera) containing a
sole lineage inhabiting mammal nests; chewing lice and sucking lice (Phthiraptera),
composed of four major clades parasitic on birds and principally mammals; and
bugs (Hemiptera), consisting of three blood-feeding lineages. Holometabolous parasites are beetles (Coleoptera), of diverse parasitic life habits; fleas (Siphonaptera),
whose modern lineages likely form a clade with older mid-Mesozoic giant fleas;
flies (Diptera), with blood feeding possibly originating in the Triassic; erebid moths
(Lepidoptera) that convergently evolved stylate mouthparts for blood feeding; and
wasps (Hymenoptera), with few parasites but an inordinate proliferation of
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution
Feener and Brown 1997). These data may indicate that for parasitoids, host breadth
of intermediate selectivity would be favored (Ferns and Jervis 2016), generating
specialists and generalists on opposite sides of the host specificity continuum.
11.9 Summary and Conclusions
Many extant and extinct insects are predators, parasites or parasitoids. However,
explicit recognition of parasitoidism as a distinct ecological process on par with
predation and parasitism has been a relatively recent development. Parasitoidism
historically was categorized by its location on the host (ectoparasitoidism versus
endoparasitoidism), by presence on the same host individual of multiple conspecifics (superparasitoidism) or by multiple non-conspecifics (multiparasitoidism).
Other descriptive designations common in the parasitoid literature are hyperparasitoidism, the condition of parasitoids living on other parasitoids, and cleptoparasitoidism, the killing of a host individual resulting from a parasitoid absconding food
or other vital resources. Direct and indirect evidence for predation, parasitism and
parasitoidism in the fossil record consists of biomolecular data, taxonomic affiliations, morphological and functional attributes, gut contents and coprolites of body
fossils, in addition to host-tissue damage, plant–insect interactions and sedimentary
structures of trace fossils. Parasite and parasitoid insect clades overwhelmingly
have targeted 84 clades of holometabolous insects and minimally targeted 4 clades
of hemimetabolous insects. The accumulation curve of originations for parasitoid
larval dietary substrates through geologic time records a major upward trend, in
contrast to more gently increasing trends for fungivory, phytophagy and predation.
Contrary to parasitoid evolutionary trajectories, the larval dietary trajectory for
ectoparasites resulted in evolutionary cul-de-sacs that did not lead to major diversification events. Parasitoids from three orders of insects—beetles (Coleoptera), flies
(Diptera) and wasps (Hymenoptera)—document the multiple and complex paths
that various lineages transit into and out of the parasitoid life habit.
Parasites and parasitoids have fossil records ranging from poor to fair, although
their modern diversities can be very elevated. Ten groups of parasites occur among
hemimetabolous and holometabolous insects. Hemimetabolous parasites are cockroaches (Blattodea) consisting of an extinct fossil lineage; earwigs (Dermaptera),
with two lineages parasitic on bats and rodents; bark lice (Psocoptera) containing a
sole lineage inhabiting mammal nests; chewing lice and sucking lice (Phthiraptera),
composed of four major clades parasitic on birds and principally mammals; and
bugs (Hemiptera), consisting of three blood-feeding lineages. Holometabolous parasites are beetles (Coleoptera), of diverse parasitic life habits; fleas (Siphonaptera),
whose modern lineages likely form a clade with older mid-Mesozoic giant fleas;
flies (Diptera), with blood feeding possibly originating in the Triassic; erebid moths
(Lepidoptera) that convergently evolved stylate mouthparts for blood feeding; and
wasps (Hymenoptera), with few parasites but an inordinate proliferation of
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution