Gasteruption barnstoni

Distinguished from ichneumon wasps by fewer antennal segments (13–14 vs. many more in ichneumons). Separated from sphecid wasps such as Ammophila by the high attachment of abdomen on thorax and swollen hind tibiae. The combination of pronounced neck, enlarged hind tibiae, and high abdominal attachment is diagnostic for Gasteruptiidae. Species-level identification requires examination of thoracic sculpturing and coloration; G. barnstoni specifically is one of five eastern North American species in the genus.

Slender wasp with elongated petiole creating a pronounced 'neck' between head and thorax. Abdomen attached high on thorax, not between hind legs. Hind tibiae distinctly swollen, appearing enlarged relative to other leg segments. Antennae with 14 segments in females, 13 in males. Ovipositor in females notably long, sometimes with white tip. Body length ranges 13–40 mm, with much of female length due to ovipositor. Overall appearance described as 'flying needle' due to extreme slenderness. Species-level identification requires examination of thoracic texture and color pattern details.

Associated with habitats supporting solitary bees and wasps that nest in twigs or wood borings. Adults frequently encountered at flowers, particularly umbelliferous plants in Apiaceae. Also observed at White Sweet Clover (Melilotus alba), Desert Broom (Baccharis sarothroides), and Leafy Spurge (Euphorbia esula).

Eastern North America, including eastern United States and Canada. One of five Gasteruption species occurring in this region.

Flight activity peaks in late spring (latter half of May) and mid-summer (July), based on observations of eastern North American Gasteruption species.

• Solitary bees - parasitoidParasitoid of solitary bees nesting in twigs or wood borings. Female deposits egg in host nest using long ovipositor.

Female deposits egg in host nest tunnel. Larva hatches and feeds on pollen, nectar, or prey provisions stored for host larva, rather than consuming the host larva directly. Developmental details otherwise poorly documented.

Females exhibit vertical and horizontal leg-swaying behavior during flight near host nests, hypothesized to tune into vibrational signals from hosts. Hind legs dangle conspicuously during flight. Adults visit flowers for nectar. Does not sting.

Parasitoid of solitary bees, regulating populations of soil-nesting and twig-nesting bee species. Adult flower-visiting behavior may contribute to pollination.

Non-stinging wasp that may benefit from mimicry of stinging wasp species. Potential use in biological study of host-parasitoid relationships. No documented economic impact.

• Ichneumon waspsSimilar slender build, but distinguished by fewer antennal segments (13–14 vs. many more) and enlarged hind tibiae
• Ammophila (Sphecidae)Similar appearance but differs in abdominal attachment position and lacks swollen hind tibiae

• parasitoid
• bee parasite
• carrot wasp
• eastern North America

• BugGuide
• iNaturalist taxon
• Gasteruption longipleurale - Entomology Today
• Balance, Hearing, and More: Why Some Wasps Have Fat Lower Legs
• Bug Eric: Wasp Wednesday: Carrot Wasps