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Anaphes flavipes
(Hymenoptera: Mymaridae)

by Richard Bean and Ashley Ciaglo, Maryland Department of Agriculture, Plant Protection Section, 50 Harry S. Truman Parkway, Annapolis, MD 21401

Anaphes flavipes is a parasitoid wasp that was introduced to the United States from Europe in 1965 for the control of the cereal leaf beetle, Oulema melanopsis L. (Coleoptera: Chrysomelidae).

Appearance

Anaphes flavipes is a minute (approximately .75 mm) chalcidoid wasp with greatly reduced venation in the forewings. The antennae are long and slender and are used to distinguish the sex of the wasp. The males are characterized by filiform, 12-segmented antennae, where the females have clavate 9-segmented antennae. The tarsi are 4 or 5 segmented. Females are generally more active than males, walking briskly with their antennae in alternating but constant tapping motions.

Habitat

Usually found in small grains fields or in adjacent hedges or fence rows. The wasps' overwinter habits are presently unknown.

Pests Attacked (Host Range)

Oulema melanopsis (cereal leaf beetle) is the main host; however Anaphes is also known to parasitize O. gallaeciana, Lema collaris, and Lema trilineata (three lined potato beetle) if the primary host is not available. Techniques have been developed using L. trilineata eggs for laboratory rearing of A. flavipes. With the exception of the four species listed previously, Anaphes will oviposit in eggs of other Chrysomelidae, but development doesn't proceed much beyond embryogenesis.

Life Cycle

Anaphes can have on average 2 generations per year, although as many as 8 have been observed on Oulema. Their life cycle consists of the egg, larvae, prepupa, pupa, and adult stages. The egg stage consists of the internal cleavage of the parasitoid and its growth into a larva. The larval stage consists of the consumption of the host's egg yolk. As a prepupa, the parasitoid is completely motionless; the excretion of the fecal matter signifies the end to this stage. In the early pupal stage, the red compound eyes are the first feature visible. The body begins to darken and faint adult characteristics become visible.

A. flavipes early pupal stage within host. Red compound eyes are the first visible feature. PHOTO: USDA, APHIS, PPQ, Niles Plant Protection Center		A. flavipes late pupal stage within host. Note the darkened body. PHOTO: USDA, APHIS, PPQ, Niles Plant Protection Center

In the late larval stage the body is dark and the ovipositor is visible on the female. Just before emergence the head and legs show movement as the parasitoid chews its way through the egg chorion. Under ideal conditions (21-25°C) the adults emerge from the host egg in 10 to 11 days. A minimum of 174 hours (at 32.2°C) to a maximum of 1089 hours at (2.7°C) was determined for the development of Anaphes from egg to adult. Within one hour after emergence, adult female Anaphes will attack suitable hosts and commence egg deposition. On average, females deposit 20 eggs during an average 2-3 day post emergence period. Females will deposit fertilized (resulting in female offspring) and non-fertilized eggs (which result in male offspring).

Studies have indicated that when Oulema eggs are most abundant, cool temperatures are prevalent. These cool temperatures are not conducive to the rapid development of Anaphes and may be another explanation for the time lag between host and parasitoid activity.

Relative Effectiveness and Conservation

A. flavipes is one of two parasitoids that have been successfully established for cereal leaf beetle control. An equilibrium where the cereal leaf beetle was kept to controllable levels lasted until the late 1980's in Maryland when surveys found the natural enemies absent or with very low populations. This prompted a renewed release effort that is being continued today.

Alone, A. flavipes is usually unable to reduce host populations below an economically acceptable level. The original efforts of USDA that introduced a complex of parasitoids to control cereal leaf beetle was quite successful. This complex includes the larval parasitoids Diaparsis temporalis, Lemophagus curtus, and Tetrastichus julis .

The effectiveness of this parasitoid remains fairly low during peak cereal leaf beetle activity. This is attributable to a lack of synchronization between the parasitoid and its host. Measures to minimize this asynchronization are to avoid a heavy layer of ground litter as this may trap the parasites as they emerge. Also, a heavy cover may delay soil warm-up, attributing to the delay in parasite emergence.

It is suggested by Anderson that the A. flavipes may be sustained through the late summer and fall by eggs of Oulema that were deposited on marginal grasses. He noted a state of diapause and assuming this, he reasoned that one egg containing two females and one male would be sufficient to maintain the species and create a small focus of parasites on the margins of wheat fields in the spring.

Oulema eggs (at 21°C) are susceptible to parasitization up to 115 hours after deposition. Between 118-120 hours, Anaphes will lay eggs, but neither parasitoid nor host develops. The parasitoid will develop successfully in host eggs that are 115-118 hours old, but the time for development and emergence is retarded. If the development in the host egg has progressed to where the mandibular structures of the beetle embryo have sclerotized, the parasite will retract its ovipositor and not parasitize the egg.

Pesticide Susceptibility

Pesticide applications are detrimental to A. flavipes and thus to successful biological control of its host.

Commercial Availability

Not available commercially. Contact either USDA or your State Department of Agriculture to determine if a rearing project exists in your state.

References

Anderson, R.C. 1968. The biology and ecology of Anaphes flavipes (Foerster) (Hymenoptera: Mymaridae), an exotic egg parasite of the Cereal Leaf Beetle (Coleoptera: Chrysomelidae). Ph.D. Thesis, Purdue Univ., 148 pp.

Anderson, R. C. and J. D. Paschke. 1968. The biology and ecology of Anaphes flavipes, an exotic egg parasite of the cereal leaf beetle. Ann. Entomol. Soc. Amer. 61: 1-5.

Burger, et al. 1978 Cereal Leaf Beetle parasitoid workshop. Handbook, USDA, APHIS. Cereal Leaf Beetle rearing lab, Niles, Mi.

Burger, et al. 1994 Cereal Leaf Beetle Biocontrol Project - FY 1994 Project Report. USDA, APHIS, PPQ National Biocontrol Laboratory, Niles, MI.

Staines, C. L. 1984. Cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae): Density and parasitoid synchronization study in Washington County, Maryland 1977- 1979. Proc. Entomol. Soc. Wash. 86: 435-438.

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