Hosts or Prey
Larvae (caterpillars) of butterflies and moths, such as navel orangeworm
Identification
The most obvious evidence that Copidosoma or a related wasp is present is the change in appearance of parasitized caterpillars because the wasps themselves become visible through the host covering. The wasp larvae are pale so they can cause a parasitized caterpillar to appear lighter colored than healthy caterpillars. Caterpillars containing Copidosoma adults or pupae darken because these wasp stages are blackish.
Adult Copidosoma are about 1/16 inch (1.5 mm) long and black, dark green, or purplish wasps. The wings are clear with one vein along the front edge.
Eggs, larvae, and pupae occur inside the host. The pale to translucent eggs are teardrop shaped with a long tail-like stalk at the narrow end. The parasitoid larvae that will develop into reproductive adults are maggotlike. Copidosoma also commonly produce a second type of larva called a soldier. Soldiers are more slender and elongate and have enlarged mouthparts.
Pupae are oblong and initially pale but darken and become apparent through the host covering as they mature into adults. Each wasp pupa occurs within a clear, thin cocoon that can be visible through the host covering.
Life Cycle
Copidosoma species develop through four life stages egg, larva, pupa, and adult. Varying by species the mated adult female lays one to a several embryos (immature "eggs") in the egg or larva of its host. Fertilized embryos develop into female parasitoids and unfertilized embryos become males. Commonly one embryo of each gender is laid in a host.
Copidosoma are polyembryonic wasps, meaning a single parasitoid embryo will clone itself into numerous siblings varying by species from a couple dozen to hundreds of individuals. For example, 1 embryo of C. bakeri can become more than 1,000 wasps. Copidosoma truncatellum develops as many as 3,000 individuals from a single embryo.
If the parasitoid embryo is laid in the egg stage of a host the parasitoid remains inactive until the caterpillar hatches. Each parasitoid embryo develops into intermediate tissues (morula, polygerm) that become numerous immature parasitoids. Once the host develops to a late instar (larva) or pupa, the parasitoids become larvae that consume the host's body contents as they develop through four or five increasingly larger instars.
Once the host is killed and consumed the parasitoid larvae pupate within the host's skin. The adult parasitoids then emerge and mate. Then the adult females begin searching for host eggs or caterpillars in which to lay their embryos.
At least some Copidosoma species (e.g., C. floridanum, C. koehleri, C. truncatellum) have a cast system with two different types of larvae. Larvae either develop into reproductive adults as described above or become soldiers. Cloned embryos that become soldiers develop into larvae soon after the host begins feeding. The soldiers patrol the host's inside and attack and kill any larvae of other wasp species or flies (e.g., Tachinidae) that also parasitize the host.
Soldiers may also kill some of their siblings. For example, if the parent parasitoid laid an egg that develops into female parasitoids and a second egg that develops into males, the female soldiers commonly kill many of the immature male parasitoids. This results in more food (the host) available for the development of female wasps. Once the reproductive cast Copidosoma complete their development the soldier larvae die without ever maturing into adults.
Development time from an egg to a reproductive adult is about 1 month when temperatures are warm. Copidosoma can have several generations per year as long as their hosts are available.
Habitat
Copidosoma plethoricum was introduced from Mexico along with a second parasitoid, Goniozus legneri, from Argentina and Uruguay to help control navel orangeworm, a primary pest of almonds. Both parasitoids are now found in orchards throughout California. Copidosoma can occur in field and tree crops, landscapes, and wildlands wherever their host caterpillars are found.
To improve biological control
- Control ants because they attack natural enemies of various pests.
- Grow flowering insectary plants to provide nectar 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.
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
At least 17 species of Copidosoma occur in California and parasitize various species of moth larvae. For example C. truncatellum parasitizes at least 68 species of caterpillars, mostly those in the family Noctuidae (armyworms and cutworms).
More Information
- Annotated Checklist of California Encyrtidae (Hymenoptera) (PDF), UC Berkeley, Zootaxa
- Developmental Patterns in the Polyembryonic Parasitoid Wasp Copidosoma koehleri, Arthropod Structure & Development, Elsevier
- Polyembryony in Copidosoma koehleri Blanchard, UC Riverside, The American Naturalist
- Universal Chalcidoidea Database, The Natural History Museum, London
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Encyrtidae
