Hosts or Prey
Identification
Obvious evidence of the activity of this tiny fly is the presence of cottony cushion scale nymphs and adult females with a rounded emergence hole left by the adult fly. Sometimes the fly pupates externally because it emerged from the host as a mature larva. If so the black, dark red, orange, or yellow fly puparium (covering of the pupa) may be observed attached to the scale it killed during the parasitoid's larval stage.
The Cryptochaetum adult is a dark, blackish to metallic blue fly with 1 pair of short, round-tipped, translucent grayish wings. The body is stout and about 1/16 inch (1.5 mm) long in males and 1/12 inch (2 mm) long in females.
Eggs are 1/125 inch (0.2 mm) long and slightly kidney shaped (elongate with a notch) to oblong. They are laid hidden inside the host.
The larva is cylindrical, distinctly segmented, and orange or yellow. It grows 1/8 to 1/6 inch (3–4 mm) long. Second through fourth instars develop 2, tail-like breathing tubes (spiracles) of variable length up to 4 times the body length.
The prepupa and puparium are oblong and 1/12 to 1/8 inch (2–3 mm) long. The puparium initially is yellow, then darkens to orangish then dark red to blackish. Two short, breathing tubes (spiracles) protrude from the rear end of puparium.
Life Cycle
Cryptochaetum develops through four life stages: egg, larva, pupa, and adult. After hatching from an egg, the larva develops through four increasingly larger instars while feeding inside a cottony cushion scale.
After pupating, emerging as an adult, and mating the adult female Cryptochaetum lays one to ten eggs into a host depending on the host size. The fly larvae feed, mature, and pupate inside the host they killed, but sometimes the mature fly larva emerges and pupates outside the host.
Egg to adult development requires about 1 month when temperatures are warm. Cryptochaetum iceryae has about 5 generations per year in California.
Habitat
Cryptochaetum iceryae and vedalia, Novius (=Rodolia) cardinalis a lady beetle (ladybug or ladybird beetle), were imported from Australia to California in the late 1880s to control cottony cushion scale infesting citrus. They provide complete biological control of cottony cushion scale on most hosts in California and elsewhere in the world where they have been introduced, unless disrupted by adverse conditions, such as the application of certain insecticides.
Cryptochaetum is the predominate natural enemy of cottony cushion scale in coastal areas of California. Its reproduction and survival is reduced by the summer heat and low humidity at interior locations. Vedalia is the most important biological control of cottony cushion scale in the Central Valley and desert areas of California. Both natural enemies can be common at intermediate locations, such as the delta regions of the Sacramento and San Joaquin Rivers.
To improve biological control
- Control ants because they attack natural enemies of scale insects and other 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 irrigation 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
Over 40 Cryptochaetum species are known in the world. The group is native to Asia and Australia. Several species including Cryptochaetum iceryae, C. grandicorne, C. jorgepastori, and C. monophlebi have been introduced in various countries to control scale insects.
More Information
- Bioecological and Population Studies of the Cottony Cushion Scale, Icerya purchasi Mask., and Its Natural Enemies, Rodolia cardinalis Muls., and Cryptochaetum iceryae Will., in Southern California, UC Riverside, Hilgardia
- The Biology, Post-embryonic Development, and Economic Importance of Cryptochaetum iceryae (Diptera, Agromyzidae) Parasitic on Icerya purchasi (Coccidae, Monophlebini), Journal of Zoology
- The Biology and Development of Cryptochaetum grandicorne (Diptera), an Internal Parasitoid of Guerinia serratulae (Coccidae), Journal of Cell Science
- Diptera, Agromyzidae: Description & Statistics [Cryptochaetum iceryae], UC Riverside
- Introduced Parasitoids and Predators of Arthropod Pests and Weeds: A World Review, U.S. Department of Agriculture
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Diptera
- Family: Cryptochaetidae
