''Stephanus serrator'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of parasitic wasp in the family

Stephanidae The Stephanidae, sometimes called crown wasps, are a family of parasitoid wasps. They are the only living members of the superfamily Stephanoidea. Stephanidae has at least 345 living species in 11 genera. The family is considered cosmopolitan in ...

, the crown wasps. This species is native to much of Europe and is to be seen in the breeding season on recently dead timber or wood products. The larvae are

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

s of the larvae of wood-boring

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

Description

Stephanid wasps are known as crown wasps because the top of the wasp's head bears a group of five tubercles. The somewhat elongated

prothorax The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on ea ...

is connected to the

propodeum The propodeum or propodium is the first abdominal segment in Apocrita Hymenoptera (wasps, bees and ants). It is fused with the thorax to form the mesosoma. It is a single large sclerite, not subdivided, and bears a pair of spiracles. It is strongl ...

(the first abdominal segment) by a very long petiole, and the ventral side of the hind femur bears teeth. The male ''S. serrator'' averages in length and the female , with an

ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...

of . The slender body and legs are black, apart from the front half of the abdomen and certain leg segments, which are red.

Distribution

''S. serrator'' is known from Spain, France, Netherlands, Italy, Germany, Switzerland, Austria, Czech Republic, Hungary, Romania, Bulgaria, Croatia, Serbia and Montenegro. Adults can be found on and around trees that have been dead for about a year and which contain beetle larvae, but which have not yet been invaded by

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

; this wasp has been recorded parasitising several different

host species In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

. It is usually found in forests or other rural locations, but when recorded from Romania for the first time in 2015, the wasps were found on a timber shed in an urban environment. Other non-natural habitats where it has been observed include fencing, utility poles, wooden boarding and stacked firewood, in each case attracted by beetle larvae within.

Ecology

''S. serrator'' is a

of the larvae of wood-boring

s. Despite being able to fly, these wasps usually move about by walking and usually avoid sunlight. Spiders such as ''

Nuctenea umbratica ''Nuctenea umbratica'', the walnut orb-weaver spider, is a species of spider in the family Araneidae. Name The species name ''umbratica'' means "living in the shadows" in Latin. Description The walnut orb-weaver spider is very wide and flatte ...

'' and '' Parasteatoda'' spp. sometimes feed on the wasps, but the wasps usually manage to evade them. Female wasps that are trying to locate beetle larvae in wood adopt a characteristic posture with fore and hind legs spread widely, middle legs folded tightly against the body, antennae lowered and ovipositor sheath pressed against the wood; they then move a few centimetres to a new location and repeat the process. When a potential target is located, the ovipositor is bored into the substrate. Boring may take many hours, with rests in between the boring efforts, at which times the females withdraw their ovipositors. They seem to be able to re-locate the hole they were working on when they recommence boring. As the ovipositor is pushed deeper into the wood, the sheath arches upwards in a loop. The eggs are laid in the galleries created by the beetle larvae. The developing wasp larvae feed on the beetle larvae, rejecting the most heavily

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

ised parts. When fully developed they pupate in the galleries left by the beetle larvae. Male wasps emerge some ten days before the females and adopt a similar search posture, perhaps waiting for the females to emerge.

References

{{Taxonbar, from=Q14855828 Stephanoidea Hymenoptera of Europe Insects described in 1798 Taxa named by Johan Christian Fabricius