Hosts or Prey
Scale insects mostly
Identification
Obvious activity of a Metaphycus species or its relatives is a round hole in a crusty, puffy covering of a mummified scale. This demonstrates the scale was parasitized and killed by a tiny wasp. The covering of parasitized scales commonly changes color because immature parasitoids are visible through the host covering, parasitoid mummification causes of the host cuticle (covering) to discolor, or both.
Adult Metaphycus are mostly brown, orange, or yellow wasps about 1/32 to 1/10 inch (0.8–2.5 mm) long varying by gender, nutrition, and species. Their clear wings have one slightly branched main vein along the front of the forewings. Adults have bulging eyes that are commonly greenish.
Eggs, larvae, and pupae occur hidden inside the host. The pale eggs are oblong. Eggs and first instars are about 1/100 inch (0.25 mm) long. First instars are saclike, almost spherical. Second through last (fourth) instars are legless and maggotlike with distinct segments. Last instars and pupae are about 1/20 inch (1.2 mm) long, but this varies for example according to host size and how many Metaphycus a scale contains. As the oblong pupae age, distinct appendages develop folded against the body.
Life Cycle
Metaphycus species develop through 4 life stages: egg, larva, pupa, and adult. The mated adult female lays 1 to several eggs in a host. Females live for 1 to several weeks during which each wasp can lay several dozen eggs. The hatching wasp larvae develop through 4 increasingly larger instars while feeding inside the host's body. Metaphycus species can have multiple generations per year.
In addition to killing hosts by parasitizing them, adult female Metaphycus host feed. Females puncture scales with their ovipositor and consume the exuding body contents. Host feeding increases parasitoid longevity and the abundance of eggs laid and kills scales without any parasitoid eggs being laid in them.
Habitat
Metaphycus species occur throughout California on almost any tree crop or woody landscape or wildland plant infested with their hosts.
Commercial Availability
Certain Metaphycus species may be commercially reared and sold for release, such as to control soft scales in greenhouses and interiorscapes. To conserve resident natural enemies and any that are released
- Control ants because they attack natural enemies of scales and other pests.
- Grow flowering insectary plants to provide nectar and pollen to nourish adult natural enemies.
- Reduce dustiness that disrupts the activities of natural enemies (e.g., irrigate overhead or periodically hose off small plants).
- Avoid the application of broad-spectrum, persistent insecticides for all pests because they are toxic to natural enemies.
See The Association of Natural Biocontrol Producers, Biological Control Organisms for Insects and Mites (PDF), Natural Enemy Releases for Biological Control of Crop Pests, Protecting Natural Enemies and Pollinators, and Selectivity of Insecticides and Miticides for more information.
Species
At least 32 species of Metaphycus occur in California. Soft scales (family Coccidae) are their most common hosts. Most Metaphycus have multiple host species. For example, M. helvolus parasitizes at least 22 species of scales. Some Metaphycus species parasitize hosts in other scale families including Diaspididae, Eriococcidae, or Kermesidae. Certain mealybugs and psyllids are hosts of some Metaphycus species.
More Information
- Augmentative Release Trials with Metaphycus spp. (Hymenoptera: Encyrtidae) Against Citricola Scale (Homoptera: Coccidae) in California’s San Joaquin Valley, UC Riverside, Journal of Economic Entomology
- Annotated Checklist of California Encyrtidae (Hymenoptera) (PDF), UC Berkeley, Zootaxa
- California Metaphycus, a key to the species, UC Berkeley
- Metaphycus alberti – Hymenoptera: Encyrtidae, Cornell University
- Universal Chalcidoidea Database, Natural History Museum of London
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Encyrtidae
