Natural Enemies Gallery

Leafminer Diglyphus Parasitoids

Hosts or Prey

Larvae of certain family Agromyzidae leafminers including Agromyza, Liriomyza, and Phytomyza spp.

Identification

Except for the adult all life stages of Diglyphus occur hidden within leaf mines. If the wider end of a leaf mine containing Diglyphus is viewed back lit, a parasitoid larva or pupa may be visible through the leaf surface.

The adults are wasps 1/16 to 1/12 inch (1.5–2 mm) long. The body is dark metallic blue or green but commonly appears blackish. The legs are black and yellowish. The 2 pairs of wings are clear and the front margin of forewings has a distinct long vein with a short branch. The presence of 4 tarsal (feet) segments and 1 straight spur (spine) on the tibia (longest leg segment) where it meets the tarsus (feet) distinguish adult Eulophidae from all other families of wasps.

The cylindrical eggs are slightly curved and translucent. Larvae are bluish green, green, or yellowish, legless maggots up to 1/10 inch (2.5 mm) long. The oblong pupae are initially pale, then become green or yellowish with red eyes. As the wasp ages and matures into an adult it darkens and distinct appendages become apparent folded against the body.

Life Cycle

Diglyphus species develop through four life stages: egg, larva, pupa, and adult. Except for adults, all life stages occur in plant tissue where their host feeds. The adult female wasp inserts her ovipositor into a leaf mine, punctures the leafmining larva with her ovipositor, and injects venom that paralyzes the host. She then lays one or more eggs on or adjacent to the fly larva. After hatching the wasp larvae develop through three increasingly larger instars as they sucking feed externally on the paralyzed host.

The mature wasp larva (prepupa) excretes about six pellets of black meconium (feces) that surround where it will pupate. These pellets act as pillars that keep the upper and lower leaf surfaces separated during pupation. Pupae occur naked in the leaf mine without forming a cocoon. The Diglyphus pupa occurs near the shrunken skin of the fly larva it consumed and killed.

In addition to killing hosts by parasitization the adult female wasp kills hosts to feed on them. She punctures leafmining larvae with her ovipositor and host feeds on the exuding body contents. A single female wasp can feed on and kill several dozen fly larvae during her lifetime in addition to the several dozen eggs she lays that become fly-killing, parasitoid larvae.

If hosts are present Diglyphus can develop and reproduce throughout the year where winters are mild. Egg to reproductive adult development occurs in about 2 weeks when temperatures are warm. Diglyphus species have multiple generations per year.

Habitat

Diglyphus can be found anywhere plants are infested with its leafmining hosts. The plants mostly likely to be significantly damaged by leafminers are mostly herbaceous annual crops and ornamentals.

Commercial Availability

Some species (e.g., D. isaea) are commercially reared and sold for release in greenhouses to biologically control Agromyzidae leafminers. If release of commercial Diglyphus is being contemplated and to conserve any resident natural enemies

  • Control ants because they attack natural enemies of various 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., overhead irrigate 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 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 the table of relative toxicities of insecticides and miticides to natural enemies and honey bees for specific crops.

Species

At least 6 species of Diglyphus occur in California: Diglyphus begini, D. carlylei, D. intermedius, D. isaea, D. pulchripes, and D. websteri. Each parasitizes multiple species of fly larvae. For example D. begini parasitizes at least 25 species of Agromyzidae. Diglyphus isaea parasitizes at least 18 species of Agromyzidae.

More Information

Scientific classification:

  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Hymenoptera
  • Family: Eulophidae
Bluish green larva of <i>Diglyphus begini</i> (center) feeding on a yellow leafminer larva obscured by its dark excrement.
Bluish green larva of Diglyphus begini (center) feeding on a yellow leafminer larva obscured by its dark excrement. Credit: Jack Kelly Clark, UC IPM
Larva of <i>Diglyphus begini</i> exposed in a leaf mine.
Larva of Diglyphus begini exposed in a leaf mine. Credit: Jack Kelly Clark, UC IPM
Pupa of <i>Diglyphus begini</i> exposed in a leaf mine.
Pupa of Diglyphus begini exposed in a leaf mine. Credit: Earl R. Oatman, UC ANR
Adult <i>Diglyphus isaea</i>, a parasitoid wasp of leafminers.
Adult Diglyphus isaea, a parasitoid wasp of leafminers. Credit: Joseph Berger, Bugwood.org Licensed under a Creative Commons Attribution 3.0 License.
Adult <i>Diglyphus</i> species wasp.
Adult Diglyphus species wasp. Credit: Ken Schneider, California Academy of Sciences. Licensed under a Creative Commons Attribution-NoDerivs-NonCommercial 1.0 Generic License.
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