Hosts or Prey
Woolly whitefly
Identification
The easiest way to recognize when A. spiniferus or its relatives are present is to examine fourth instars (pupae) of woolly whitefly. When A. spiniferus is present pupae are blackish to orangish because the body of the immature wasp is visible through the covering of the whitefly and the parasitoid's mummification of the whitefly causes its covering to darken. When an adult A. spiniferus emerges from a whitefly it killed it leaves a rounded hole in the pupa and the covering is brown to orangish and contains pellets of excrement (meconium). When a whitefly emerges from its pupal case the covering is more whitish and empty (contains no meconium) and has a ragged or T-shaped slit.
Adult A. spiniferus are about 1/25 inch (1 mm) long. They have clear wings, a black head and body, and black and yellowish antennae and legs.
Eggs, larvae, and pupae of the parasitoid occur only in the body of woolly whiteflies. Eggs are elongate spherical with a stalk. Eggs and larvae are orangish. The initially orangish pupae blacken as they age. A larva or pupa of the wasp can be visible through the host covering.
Life Cycle
Amitus spiniferus develops through 4 life stages: egg, larva, pupa, and adult. The wasp is parthenogenetic and reproduces without mating. Adult female wasps prefer to oviposit in first and second instar whitefly nymphs and the adult wasp emerges from the whitefly's pupal stage. Adult wasps live for about 2 to 3 weeks during which a female can lay several hundred eggs.
After hatching from an egg A. spiniferus larvae develop through 3 increasingly larger instars as they consume the body contents of the whitefly. Egg to adult development is about 3 weeks when temperatures average 77ºF. Amitus spiniferus has several generations per year.
Habitat
Woolly whitefly is an exotic species that invaded California from Mexico in the 1960s. It infests a wide range of crops and ornamental plants and especially was a problem on citrus.
Entomologists from the California Department of Food and Agriculture, University of California, and U.S. Department of Agriculture conducted foreign exploration to collect natural enemies of the whitefly as part of a classical biological control program. Researchers collected Amitus spiniferus in Mexico and after study in quarantine revealed the wasp preys only on woolly whitefly, A. spiniferus was introduced into California during 1967 to 1970.
Woolly whitefly is now under complete biological control due to parasitism by A. spiniferus in combination with another parasitic wasp, Cales noacki, which was introduced from Chile in 1970. Exceptions are when these natural enemies are disrupted by very cold or hot temperatures or the application of broad-spectrum, persistent insecticides.
Species
At least three Amitus species occur in California: A. aleurodinis, A. arcturus, and A. spiniferus. Woolly whitefly is the only reported host of A. spiniferus.
More Information
- Biological Control of Woolly Whitefly, California Agriculture
- Population Dynamics and Biological Control of the Woolly Whitefly (Homoptera: Aleyrodidae) on Citrus, UC Riverside, Environmental Entomology
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Platygastridae
