Perilampus platigaster

Distinguished from similar small metallic wasps, particularly cuckoo wasps (Chrysididae), by the triangular or pyramidal abdomen with sharp corners (cuckoo wasps have oval or rounded abdomens without sharp corners) and short, strongly elbowed antennae. The compact body form and metallic coloration can cause confusion with chrysidids, especially when both are found near aphid colonies or sunflower extrafloral nectaries.

Compact body measuring 1.3–5.5 mm in length. Abdomen shaped like a triangle or inverted pyramid with distinct corners, not oval or rounded. Short, strongly elbowed antennae. Coloration variable: many individuals brilliant metallic green or blue, others wholly black.

Found in vegetation where hosts occur, including plants with aphid colonies and sunflowers with extrafloral nectaries. Eggs are laid on leaves, buds, cracks in bark, under lichens, and similar substrates where planidium larvae might encounter hosts.

Recorded from Colorado, Connecticut, District of Columbia, Florida, and Illinois in the United States.

Larval stage is parasitic, typically hyperparasitic on other parasitoids including tachinid flies, ichneumon wasps, and braconid wasps. Some perilampids in the subfamily Perilampinae can develop as primary parasites on secondary hosts when primary hosts are absent, but whether P. platigaster specifically exhibits this flexibility is not documented.

• Tachinidae - parasitoidlarvae parasitize tachinid fly larvae
• Ichneumonidae - parasitoidlarvae parasitize ichneumon wasp larvae
• Braconidae - parasitoidlarvae parasitize braconid wasp larvae
• Lepidoptera - indirectsecondary hosts (caterpillars) contain the primary parasitoid hosts

Female broadcasts 500 or more eggs on vegetation and substrates. First instar is a flattened, mobile planidium that attaches to moving objects with its mandibles. Successful planidia penetrate the cuticle of a secondary host (typically a caterpillar or other insect larva), then locate and enter the primary host (a parasitoid within the secondary host). The perilampid larva waits until the primary host pupates, then exits and molts into a grub-like external parasite. It passes through two or three additional instars before pupating inside the host cocoon or puparium.

Females exhibit broadcast egg-laying behavior, depositing eggs in locations where planidium larvae might encounter hosts rather than targeting hosts directly. Planidium larvae actively seek hosts by attaching to any moving object, a high-risk strategy with substantial failure rate.

Functions as a hyperparasitoid, regulating populations of primary parasitoids. This creates a tertiary trophic level in parasitoid food webs, potentially influencing biological control dynamics of herbivorous insects.

One unverified report suggests the species may bite or sting humans, though this is not documented in scientific literature and requires confirmation. The family includes species with flexible life cycles that can act as primary parasitoids, suggesting potential relevance to biological control programs.

• ChrysididaeSimilar small size, compact form, and metallic coloration. Distinguished by oval or rounded abdomen without sharp corners, versus the triangular/pyramidal abdomen of Perilampus.
• PteromalidaeTaxonomically related and historically confused with Perilampidae; classification remains debated with some authorities placing Perilampidae within or alongside Pteromalidae.

May be mistaken for flies due to relatively large eyes compared to body size. The broadcast egg-laying strategy and mobile planidium larva are unusual among parasitoids and may be misinterpreted as evidence of direct host targeting.

• parasitoid
• hyperparasitoid
• planidium
• metallic
• broadcast oviposition
• Chalcidoidea
• microhymenoptera

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
• Bug Eric: Wasp Wednesday: Perilampid Wasps