Hosts or Prey
Caterpillars of numerous moth species
Identification
Obvious evidence that Hyposoter is present is its black and white pupal cocoon. These commonly occur on foliage attached to the shriveled skin of the caterpillar in which the parasitoid fed during its larval stage. Where a Hyposoter cocoon is found, pulling apart nearby caterpillars to expose their insides may reveal a greenish wasp larva parasitizing them.
The adult wasp has long black antennae, a black head and thorax, orangish abdomen, and a narrow waist. The body is about 1/4 to 1/2 inch (6–12 mm) long varying by the size of the host caterpillar from which it emerged.
The H. exiguae larva is a pale to translucent green and occurs inside host caterpillars. The cocoon occurs on leaves and is about 1/4 inch (6 mm) long. The cocoon is oblong with dense white silk and blackish patches.
Life Cycle
Hyposoter exiguae develops through four life stages: egg, larva, pupa, and adult. It is a solitary internal parasitoid of moth larvae, especially Noctuidae (armyworms and cutworms). The adult female prefers to lay its egg in first and second instar caterpillars.
After hatching the wasp larva feeds inside on the caterpillar's hemolymph (blood) while developing through three, increasingly larger instars. The wasp larva then feeds on the caterpillar's tissues consuming the entire body except for the skin and head capsule. The host caterpillar shrinks and becomes a hard and brittle, shriveled skin. Hyposoter exiguae generally kills and emerges from caterpillars during their second, third, or fourth instar. The parasitoid emerges from the host skin as a mature third instar (prepupa). The wasp then spins a silken cocoon commonly attached to the dead caterpillar's skin.
Parasitoid development time from an egg to a reproductive adult is about 1 month when temperatures are warm. There can be several generations per year.
Habitat
Hyposoter exiguae can be found in field, tree, and vine crops, gardens, landscapes, and wildlands where any of its numerous host caterpillars occur. It is important in the biological control of caterpillars in crops including alfalfa, apricot, cherry, celery, cole crops, dry beans, lettuce, peppers, prune, small grains, strawberry, tomato, and walnut. Hosts of H. exiguae include alfalfa caterpillar, armyworms, cabbage looper, corn earworm, cutworms, tobacco budworm, tobacco hornworm, tomato fruitworm, and tussock moths.
To improve biological control
- Control ants because they attack natural enemies of various pests.
- Grow flowering insectary plants to provide nectar to nourish adult parasitoids and predators.
- Reduce dustiness that disrupts the activities of natural enemies (e.g., periodically hose off small plants or irrigate overhead).
- Avoid the application of broad-spectrum, persistent insecticides for all pests because they are toxic to natural enemies.
For more information see Protecting Natural Enemies and Pollinators and the table of relative toxicities of insecticides and miticides to natural enemies and honey bees for specific crops.
Species
Hyposoter exiguae is 1 of at least 27 Hyposoter species in the United States, most of which attack numerous species of caterpillars. The California species include at least H. annulipes, H. disippi, H. exiguae, H. fugitivus, H. fuscitarsis, H. popofensis, and H. rivalis.
More Information
- Biology of Hyposoter exiguae (Hymenoptera: Ichneumonidae), a Parasitoid of Lepidopterous Larvae, Annals of the Entomological Society of America
- Catalog of Hymenoptera in America North of Mexico. Vol. 1: Symphyta and Apocrita (Parasitica), U.S. Department of Agriculture
- Temporal Synchronization of Emergence of Hyposoter exiguae and H. fugitivus (Hymenoptera: Ichneumonidae) with Apolysis Preceding Larval Molting in Manduca sexta (Lepidoptera: Sphingidae), Annals of the Entomological Society of America
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Ichneumonidae
