Gasteruptiidae

HYMENOPTERA > APOCRITA | Parasitica > Evanioidea > Gasteruptiidae

The six members of this small family of parasitoid wasps are recognisable by their elongate form with distinctive neck-like propleura, slender subclavate (club-shaped) metasoma, swollen hind tibia and, in respect of the female of the most common species, a long, white-tipped ovipositor.

Until recently, the British List had traditionally included five species, all in the genus Gasteruption, but now, verified from an initial sighting and photograph taken in South London back in 2015 and a specimen collected and examined in 2023, a new species Gasteruption erythrostomum has been added.

None of the males can be reliably be identified from photos, which explains why so many records on both the NBN database and iRecord only relate to the genus rather than a specific species.

The most frequently recorded species is Gasteruption jaculator, described in simple terms as having a black rounded head and elongated thorax, slender abdomen with reddish-orange markings, and swollen hind tibia. The female's ovipositor is very long as can be seen in the following photos. It has a distinctive white banded tip that in European keys is said to be 1.5 - 2.7 times as long as the hind basitarsus. Adults can grow up to 17mm long, and can normally be seen from May through to September as fresh specimens emerge from the nests of different hosts.

Although confirming the identify of this particular species from photos is probably correct, there are two others that should be considered as in both cases the female has a similarly long ovipositor. The first is Gasteruption caucasicum (aka. G.pedemontanum). It's very rarely recorded, but it is widespread and common in Europe and is a distinct possibility in my area. The European key suggests that the white band is shorter than that found in Gasteruption jaculator at 0.7 - 1.6 times as long as the hind basitarsus. However, that feature can't be viewed in isolation and without a good photo of the back of the head it would be difficult to separate the two species. Yet, there is a further feature, as the mesoscutum is punctured or cratered rather than wrinkled as in Gasteruption jaculator. The other species is Gasteruption laticeps, but its inclusion is now being questioned so, for all intents and purposes, it can safely be disregarded.

The females of the remaining species all have a much shorter ovipositor sheath. The newly added Gasteruption erythrostomum is readily distinguished as the sheath is noticeably shorter than the metasoma, but at least twice as long as the hind tibia, whereas in the other two species Gasteruption assectator and minutum it is much shorter, usually shorter rather than longer than a hind tibia. Gasteruption assectator appears to be the most regularly observed based on verified records, but it can easily be confused with Gasteruption minutum, so I would have to do some more research if I manage to photograph one of these.

Previously considered to be ectoparasitoids, gasteruptiid wasps are now regarded as secondary cleptoparasitoids of food stored by various species of solitary bees, mainly of the genera Colletes and Hylaeus. The female uses her long ovipositor to penetrate the bee’s nest to lay her egg on the host larvae. After hatching, the wasp larvae will eat both its host and the food supply that the bee has collected.

Updated, July 2026 (v.3)