Parasitoids

Most parasitoids — parasitic insects that kill their hosts — live freely and independently as adults; they are lethal and dependent only in their immature stages. Parasitoids can be specialists, targeting either a single host species or several related species, or they can be generalists, attacking many types of hosts. Typically, they attack hosts larger than themselves, eating most or all of their hosts' bodies before pupating inside or outside them.

When the parasitoid emerges from its pupa as an adult, it usually nourishes itself on honeydew, nectar or pollen — although some adults make meals of their host's body fluids and others require additional water. Adult female parasitoids quickly seek out more victims in which to lay their host-killing eggs. With their uncanny ability to locate even sparsely populated hosts using chemical cues, parasitoid adults are much more efficient than predators at ferreting out their quarry.

Different parasitoids can victimize different life stages of the same host, although specific parasitoids usually limit themselves to one stage. Thus, parasitoids are classified as egg parasitoids, larval (nymphal) parasitoids or adult parasitoids. Some parasitoids lay their eggs in one life stage of a

ORDER

Díptera

(true flies)

Hymenoptera

(ants, bees and wasps)

FAMILY

Tachinidae Nemestrinidae Phoridae Crytochaetidae

Chalcididae

Encyrtidae

Eulophidae

Pteromalidae

Pteromalidae

Aphelinidae

Trichogrammatidae

Mymaridae

Scelionidae

Ichneumonidae

Braconidae

TABLE 4

Common Parasitoids*

TABLE 4

host or prey

mode of attack

Beetles, butterflies, moths

Internal

Locusts, beetles

Internal

Ants, caterpillars, termites, flies, others

Internal

Scale insects

Internal

Flies and butterflies (larvae and pupae)

Internal or external

Aphids, scales, mealybugs, whiteflies

Internal

Aphids, gall midges, sawflies, mealybugs

Internal or external

Flies, including houseflies and stable flies

Internal

Boll weevils

External

Whiteflies, scales, mealybugs, aphids

Internal or external

Moth eggs

Internal

True bugs, flies, beetles, leafhopper eggs

Internal

Eggs of true bugs and moths

Internal

Larvae or pupae of beetles, caterpillars, wasps

Internal or external

Larvae of beetles, caterpillars, sawflies

Internal (mostly)

Alfalfa weevil JfjS^

and larvae

Alfalfa weevil JfjS^

and larvae

Parasitoid/prey

Populations of the ichneumonid parasitoid, Bathyplectes curculionis, and its prey, the alfalfa weevil, fluctuate throughout the growing season.

(Reprinted with permission from Michigan Field Crop Pest Ecology, Mich. State Univ. Extension Bulletin E-2704.)

Increase parasitoids

Increase parasitoids

Parasitoid/prey

Populations of the ichneumonid parasitoid, Bathyplectes curculionis, and its prey, the alfalfa weevil, fluctuate throughout the growing season.

(Reprinted with permission from Michigan Field Crop Pest Ecology, Mich. State Univ. Extension Bulletin E-2704.)

victim but emerge at a later life stage. Parasitoids are also classified as either ectoparasites or endoparasites depending, respectively, on whether they feed externally on their hosts or develop inside them. Their life cycle is commonly short, ranging from 10 days to four weeks.

0 0

Post a comment