Hosts or Prey
Beetles, caterpillars, grasshoppers, true bugs, and certain other insects
Identification
Tachinids are the most important of the parasitic flies that provide biological control. Adults range from 1/12 to 4/5 inch (2–20 mm) long, and most are 1/8 to 1/2 inch (3–12 mm) long, varying by species. Many are blackish to gray. But some are more colorful; for example, those that resemble (mimic) bees or wasps.
A distinctive feature of adult tachinids is the abundant bristles that cover the head and body. Adults also have a shieldlike structure that covers most of the top of the thorax; this is a postscutellum of the mesothorax that is well developed and protrudes toward the rear.
Eggs are oval and transparent when laid but soon turn white. The eggs of certain species can be observed glued on the host, commonly on top the head or thorax. Eggs of other species occur hidden because the adult female of that species inserts them into the host.
Larvae are pale maggots that occur inside hosts. Because mature larvae of many species exit their host to pupate, the oblong blackish to dark reddish puparium (covering of the pupae) of tachinids can sometimes be observed, such as near a host pupa that was killed and has a distinct emergence hole of the parasitoid.
Life Cycle
Tachinids develop through four life stages: egg, larva, pupa, and adult. In most species only one larva develops per host, but in some species several larvae feed inside each host.
Mated adult females most commonly insert an egg into the host's body or glue eggs on the host's body. Others lay eggs on plants that hatch after they are consumed by the plant-feeding host insect. Others lay eggs into soil if a soil-dwelling insect is the host (e.g., root-feeding white grubs).
Most species develop through three, increasingly larger instars (larvae). First instars have especially distinct mouthparts they use to chew into the host and once inside to chew openings through the host skin through which they insert their spiracles for breathing. At maturity, the tachinid larva commonly exits the host and pupates nearby. In some species the tachinid pupates inside the host it killed.
Tachinids commonly overwinter as mature larvae inside a host insect. When the host becomes active in spring, the larva inside kills the host, pupates, then exits to seek a mate. Where winters are mild, tachinids can be active throughout the year if hosts are present. Many tachinids have several generations per year.
Erynnia tortricis parasitizes larvae and pupae of various moths. Adults are mostly gray. The adult female lays one to several eggs on the head or thorax of each host, and the hatching larvae chew downward into the caterpillar.
If several eggs are laid on a single host, only one of the tachinid larvae survives to maturity. After feeding inside, soon after the caterpillar pupates it is killed and the parasitic larva exits the pupa. Parasitized moth pupae can be recognized by the prominent Y-shaped spiracles (breathing tubes) of the parasitoid that protrude beneath the tips of the wing pads of the host pupa.
Erynniopsis antennata parasitizes the adults, larvae, prepupae, and pupae of elm leaf beetle and tamarisk beetles. The adult resembles a house fly except the body is covered with bristles.
Trichopoda pennipes is a parasitoid of true bugs (Heteroptera). Adults and mature larvae are 1/3 to 1/2 inch (8–12 mm) long. The adult has a black and yellowish prothorax (first segment behind the head), a mostly orange abdomen, and dark wings. Adult females lay oval eggs singly or in groups on the sides or top of adults or older nymphs of various true bugs.
Voria ruralis parasitizes the larvae of various species of Noctuidae and Pyralidae moths. Cabbage looper may be the most common host. Adults and mature larvae of V. ruralis are about 1/4 inch (6 mm) long. Adults are black and gray. Adult females lay one or several eggs on the host, and they hatch within minutes and chew into the host. Each female lays about 300 eggs during her lifetime. The oblong, dark red puparium are about 1/4 inch (6 mm) long. Egg to adult development time is about 3 weeks.
Habitat
Tachinids are one of the most common groups of flies. They occur in field and tree crops, gardens, landscapes, and wildlands. To improve their biological control effectiveness
- Control ants because they attack natural enemies of various pests.
- Grow flowering insectary plants to provide nectar and pollen to feed adult natural enemies.
- 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
Over 400 tachinid species are known in California. Larvae of beetles, butterflies, and moths are the most common hosts. Other hosts include centipedes, crickets, earwigs, grasshoppers, true bugs, and other flies.
More Information
- Diptera, Tachinidae (Robineau-Desvoidy 1863), UC Riverside
- A Host-Parasitoid Catalog of the North American Diptera, U.S. Department of Agriculture
- Tachinidae (PDF), In Manual of Nearctic Diptera, Agriculture Canada
- Tachinidae Resources, Agriculture and Agri-Food Canada and others
- Taxonomic and Host Catalogue of the Tachinidae of America North of Mexico, U.S. Department of Agriculture
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Diptera
- Family: Tachinidae
