The Remaining Endopterygote Orders

FIGURE 10.23. Tenthredinoidea. (A) The imported currant worm, Nematus ribesii (Tenthredinidae) adult and larva; (B) the elm sawfly, Cimbex americana (Cimbicidae); and (C) the redheaded pine sawfly, Neodiprion lecontei (Diprionidae). [A, from L. A. Swan and C. S. Papp, 1972, The Common Insects of North America. Copyright by L. A. Swan and C. S. Papp. Reprinted by permission of Harper & Row Publishers, Inc. B, C, from the U.S. Department of Agriculture.]

FIGURE 10.23. Tenthredinoidea. (A) The imported currant worm, Nematus ribesii (Tenthredinidae) adult and larva; (B) the elm sawfly, Cimbex americana (Cimbicidae); and (C) the redheaded pine sawfly, Neodiprion lecontei (Diprionidae). [A, from L. A. Swan and C. S. Papp, 1972, The Common Insects of North America. Copyright by L. A. Swan and C. S. Papp. Reprinted by permission of Harper & Row Publishers, Inc. B, C, from the U.S. Department of Agriculture.]

Superfamily Siricoidea

Female Siricoidea have a boring ovipositor, and larvae have reduced thoracic legs, no prolegs, and live in wood. The 250 species in this possibly paraphyletic group (Vil-helmsen, 2001) are divided approximately evenly among three families, XIPHYDRIIDAE, SIRICIDAE, and ORUSSIDAE. Adult siricids (horntails) (Figure 10.24) are large, often brightly colored insects found in temperate Northern Hemisphere forests. Larvae burrow extensively in the heartwood of both deciduous and evergreen trees and may cause much damage, especially those species that live symbiotically with rot-producing fungi. Though a cosmopolitan group, orussids (parasitic wood wasps) are principally tropical and Australian in distribution. Females have an extremely long ovipositor that is coiled within the body when not in use. The structure is used to lay the very elongate and thin eggs onto the body of horntail larvae and buprestid beetle larvae in their tunnels. Xiphydriidae (wood wasps)

FIGURE 10.24. Siricoidea. The pigeon tremex, Tremex columba (Siricidae). [From H. E. Evans and M. J. W. Eberhard, 1970, The Wasps. By permission of the University of Michigan Press.]

FIGURE 10.25. Cephoidea. The wheat stem sawfly, Cephus cinctus (Cephidae). [From L. A. Swan and C. S. Papp, 1972, The Common Insects of North America. Copyright 1972 by L. A. Swan and C. S. Papp. Reprinted by permission of Harper & Row Publishers, Inc.]

are similar to horntails in appearance, though usually smaller. The family is cosmopolitan (except Africa). Larvae mine in branches and small trunks of angiosperm trees and shrubs.

Superfamily Cephoidea

All Cephoidea are included in the family CEPHIDAE (stem sawflies), a largely Eurasian group of about 100 species. Larvae bore into the stems of grasses and berries. Some species are of considerable economic importance, for example, Cephus cinctus, the wheat stem sawfly (Figure 10.25), and Janus integer, which bores in the stems of currants.

Suborder Apocrita

Almost all adult Apocrita have the first abdominal segment (propodeum) intimately fused with the thorax and a constriction between the first and second abdominal segments. Larvae are apodous and have a reduced head capsule.

The first 10 superfamilies were formerly included in the Parasitica, now recognized as a paraphyletic group.

Superfamily Megalyroidea

This very small group, containing about 50 species in a single family, MEGALYRIDAE, occurs mainly in the Old World tropics. Larvae of these stout-bodied wasps are parasitoids of beetle larvae under tree bark.

Superfamily Stephanoidea

Sometimes included in the Megalyroidea, the 100 species in this group are placed in the family STEPHANIDAE, which has a tropical distribution. Adults are slender wasps with highly modified hindlegs thought to be able to detect sounds created by the wood-boring beetle larvae that serve as hosts for their larvae.

Superfamily Trigonalyoidea

Trigonalyoidea form a small (100 species worldwide) group of archaic but highly specialized Apocrita whose members are all contained in the family TRIGONALYIDAE. Structurally they possess a combination of features of Parasitica and Aculeata. The trigo-nalyids are hyperparasites of sawfly larvae or lepidopteran caterpillars. The eggs are laid

on plant tissue, which is then eaten by the sawfly larvae or caterpillars. These are then parasitized by other Hymenoptera (ichneumons) or Diptera (tachinids), which in turn become the primary host for the trigonalyids.

Superfamily Ceraphronoidea

These small (1 to 3 mm) wasps are arranged in two cosmopolitan families, MEGASPILIDAE (450 species) and CERAPHRONIDAE (360 species). The former are primary parasitoids of Coccoidea, Neuroptera, and puparia of Diptera or hyperpar-asites of aphid-infesting Braconidae. Ceraphronids, likewise, may be endoparasitoids (in Thysanoptera, Lepidoptera, Neuroptera, Cecidomyiidae, and puparia of Diptera) or hyperparasites (taken from cocoons of Braconidae). A few species have been collected in ant nests, where they are perhaps parasitoids of myrmecophilous Diptera.

Superfamily Ichneumonoidea

This group contains the two largest families of Hymenoptera, ICHNEUMONIDAE (ichneumon flies) (Figure 10.26A) with about 20,000 species (about 3500 in North America), and BRACONIDAE (Figure 10.26B), with some 35,000-40,000 species (2000 in North America). Ichneumonoids are mainly parasitoids oflarvae and pupae of endopterygotes (all orders except Megaloptera and Siphonaptera), laying their eggs either in concealed locations on the host (the primitive condition) or in the host, when various strategies are used to avoid attack by the host's immune system. Venom may be injected into the host prior to oviposition, the poison paralyzing or killing the recipient. Ichneumonids are largely restricted to juvenile stages of endopterygotes, though a few use the eggs of pseudoscorpions and spiders, or adult spiders, as hosts. Many Braconidae are parasitoids of exopterygotes,

FIGURE 10.26. Ichneumonoidea. (A) An ichneumon fly, Rhyssa persuasoria (Ichneumonidae). Note that the entire ovipositor is not drawn; and (B) a braconid, Apanteles cajae (Braconidae). [A, reproduced by permission of the Smithsonian Institution Press from United States National Museum Bulletin 216, Part 2 (Ichneumon-Flies of America North of Mexico: 2. Subfamilies Ephialtinae Xoridinae Acaenitinae) by Henry and Marjorie Townes: FIGURE 302b, pages 598. Washington D.C., 1960, Smithsonian Institution. B, from R. R. Askew, 1971, Parasitic Insects. By permission of Heinemann Educational Books Ltd.]

FIGURE 10.26. Ichneumonoidea. (A) An ichneumon fly, Rhyssa persuasoria (Ichneumonidae). Note that the entire ovipositor is not drawn; and (B) a braconid, Apanteles cajae (Braconidae). [A, reproduced by permission of the Smithsonian Institution Press from United States National Museum Bulletin 216, Part 2 (Ichneumon-Flies of America North of Mexico: 2. Subfamilies Ephialtinae Xoridinae Acaenitinae) by Henry and Marjorie Townes: FIGURE 302b, pages 598. Washington D.C., 1960, Smithsonian Institution. B, from R. R. Askew, 1971, Parasitic Insects. By permission of Heinemann Educational Books Ltd.]

notably homopterans (especially aphids), Heteroptera, Isoptera, and Psocoptera, sometimes exhibiting extremely high host specificity, but do not attack spiders. Many species are beneficial to humans because they are major natural control agents on populations of pest insects. Examples are Bracon cephi, a parasitoid of wheat-stem sawfly larvae, and several species of Apanteles and Cotesia that attack cabbageworms, the tobacco hornworm, clothes moth larvae, and gypsy moth caterpillars, among others. Several ichneumons and braconids have been used in the biological control of pests (see Table 24.6).

Superfamily Evanioidea

The constituent families are AULACIDAE (150 species worldwide), GASTERUPTI-IDAE (500 species, mainly tropical), and EVANIIDAE (400 species, mainly tropical but some species are cosmopolitan, living in buildings where their hosts occur). Aulacids are parasitoids of wood-boring larvae of Coleoptera and Xiphydriidae. Gasteruptiid females oviposit in nests of solitary bees and wasps; the larva eats the host's egg and then pollen or prey stored in the cell. Evaniids are exclusively parasites of cockroach oothecae, the larvae eating the eggs then pupating inside the host's egg case.

Superfamily Proctotrupoidea

Almost all of the approximately 2700 species in this group fall into the two families DIAPRIIDAE and PROCTOTRUPIDAE. Diapriidae (2300 species worldwide) mainly parasitize larvae and pupae of Diptera, especially of species living in moist habitats, though a few use larvae of beetles, ants, or termites as hosts. Larval proctotrupids (300 species worldwide) are mostly parasitoids of litter- or rotten wood-inhabiting beetle larvae, though a few species feed on larvae of mycetophilid Diptera.

Superfamily Platygasteroidea

Often included in the previous superfamily, the two large and cosmopolitan families that comprise the Platygasteroidea differ from the above group in the structure and operation of their ovipositor and in the structure of the female antennae. SCELIONIDAE (3000 species) are egg parasites of a wide range of insects, especially Lepidoptera, Hemiptera and orthopteroids, and spiders. Females of some species are phoretic; that is, they locate and are carried about on a suitable host until the latter begins to oviposit. The scelionid then leaves the host and lays her eggs among those of the host. PLATYGASTERIDAE (1100 species) are either egg or larval parasites, especially of Cecidomyiidae, including a number of pest species, for example, the Hessian fly, over which they exert major population control. Other hosts include cerambycids, homopterans, and sphecid wasps. Some species are polyembryonic (Chapter 20, Section 8.2), and females may be highly specific with respect to the host tissue in which an egg is laid.

Superfamily Cynipoidea

Most of the 2300 species so far ascribed to the Cynipoidea belong to the family CYNIP-IDAE, subfamily CYNIPINAE (gall wasps) (Figure 10.27), and are either gall makers or inquilines in already-formed galls. The host plant and the form of the gall are usually specific for a particular species of cynipid, though in some primitive species a range of host plants

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