397
holometabolous insect communities (Mills 1994). Mills (1994) regarded that parasitoid guilds are defined by three basic features. First, what stage of the host is
attacked by the parasitoid? Is it the egg; early, middle or late larval instar; prepupae;
pupa; or adult? Second, what is the stage of the host in which it is killed? Third, is
the mode of parasitoidism internal (endoparasitoidism) or external (ectoparasitoidism)? The 12 documented combinations of these three features that form modern
parasitoid guilds delineate ecological diversity across the seven parasitoid-bearing
orders of insects, and provide a phenomenological explanation for Rainford and
Mayhew’s (2015) conclusion of the evolutionarily dynamic nature of the parasitoid
life habit.
The three, major parasitoid harboring groups―Hymenoptera, Diptera and
Coleoptera―each display trajectories of particular lineages to and from the parasitoid life habit via particular before-and-after life-habit transitions (Poulin 2011),
indicated by arrows in Fig. 11.4a–c. For example, in Coleoptera (Fig. 11.4a),
although the thicknesses of the arrows reveal a small number of parasitoid species,
the principal movement toward parasitoidism has been from mycophagy to cleptoparasitoidism by the families Bothrideridae, Meloidae, Rhipiceridae, Ripiphoridae
and Strepsiptera (the latter clade considered a separate order in this report). A second source of movement toward parasitoidism has been from specialized egg and
clepto-provisioning predation to cleptoparasitoidism by the families Carabidae,
Cleridae, Passandridae and Staphylinidae. The principal movement away from parasitoidism has been from cleptoparasitoidism to special egg predation by the families
Cleridae and Meloidae. The patterns for Diptera (Fig. 11.4b) and Hymenoptera
(Fig. 11.4c) display a different pattern and have a greater number of trajectories,
higher numbers of transiting species, and a greater number of transiting family-level
lineages to and from the parasitoid life habit. These evolutionary shifts are explained
in more detail below for each of the three discussed insect orders.
11.5 Parasite and Parasitoid Taxa
Insect parasites and parasitoids have evolutionary and ecologically very different
life habits. The two life habits have a different set of effects on their hosts and on
themselves, based on the particular mode of extracting host resources. These different life habits may be related to the distinctive taxonomic spectra of parasites versus
parasitoids. Parasites consist of hemimetabolous lineages—Blattodea, Dermaptera,
Psocoptera, Phthiraptera and Hemiptera—that are not represented as parasitoids.
Additionally, parasites are represented by a holometabolous lineage, Siphonaptera,
which is not represented as parasitoids, and are also represented by another holometabolous lineage, Coleoptera, that is very poorly represented as parasitoids. Only
Diptera and Hymenoptera overlap significantly in containing many dominant parasite and parasitoid lineages. In comparison to parasites, the entirely holometabolous
character of parasitoids is notable, consisting of Neuroptera, Coleoptera,
Strepsiptera, Diptera, Trichoptera, Lepidoptera and Hymenoptera.
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution
holometabolous insect communities (Mills 1994). Mills (1994) regarded that parasitoid guilds are defined by three basic features. First, what stage of the host is
attacked by the parasitoid? Is it the egg; early, middle or late larval instar; prepupae;
pupa; or adult? Second, what is the stage of the host in which it is killed? Third, is
the mode of parasitoidism internal (endoparasitoidism) or external (ectoparasitoidism)? The 12 documented combinations of these three features that form modern
parasitoid guilds delineate ecological diversity across the seven parasitoid-bearing
orders of insects, and provide a phenomenological explanation for Rainford and
Mayhew’s (2015) conclusion of the evolutionarily dynamic nature of the parasitoid
life habit.
The three, major parasitoid harboring groups―Hymenoptera, Diptera and
Coleoptera―each display trajectories of particular lineages to and from the parasitoid life habit via particular before-and-after life-habit transitions (Poulin 2011),
indicated by arrows in Fig. 11.4a–c. For example, in Coleoptera (Fig. 11.4a),
although the thicknesses of the arrows reveal a small number of parasitoid species,
the principal movement toward parasitoidism has been from mycophagy to cleptoparasitoidism by the families Bothrideridae, Meloidae, Rhipiceridae, Ripiphoridae
and Strepsiptera (the latter clade considered a separate order in this report). A second source of movement toward parasitoidism has been from specialized egg and
clepto-provisioning predation to cleptoparasitoidism by the families Carabidae,
Cleridae, Passandridae and Staphylinidae. The principal movement away from parasitoidism has been from cleptoparasitoidism to special egg predation by the families
Cleridae and Meloidae. The patterns for Diptera (Fig. 11.4b) and Hymenoptera
(Fig. 11.4c) display a different pattern and have a greater number of trajectories,
higher numbers of transiting species, and a greater number of transiting family-level
lineages to and from the parasitoid life habit. These evolutionary shifts are explained
in more detail below for each of the three discussed insect orders.
11.5 Parasite and Parasitoid Taxa
Insect parasites and parasitoids have evolutionary and ecologically very different
life habits. The two life habits have a different set of effects on their hosts and on
themselves, based on the particular mode of extracting host resources. These different life habits may be related to the distinctive taxonomic spectra of parasites versus
parasitoids. Parasites consist of hemimetabolous lineages—Blattodea, Dermaptera,
Psocoptera, Phthiraptera and Hemiptera—that are not represented as parasitoids.
Additionally, parasites are represented by a holometabolous lineage, Siphonaptera,
which is not represented as parasitoids, and are also represented by another holometabolous lineage, Coleoptera, that is very poorly represented as parasitoids. Only
Diptera and Hymenoptera overlap significantly in containing many dominant parasite and parasitoid lineages. In comparison to parasites, the entirely holometabolous
character of parasitoids is notable, consisting of Neuroptera, Coleoptera,
Strepsiptera, Diptera, Trichoptera, Lepidoptera and Hymenoptera.
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution