Distribution

A. North and Central America (including Hawaii), Chile, north Africa (including the Canary Islands), Europe (excluding Iceland), Middle East, Asia, southern Australia (including Tasmania) and New Zealand.
B. Worldwide, excluding southern South America, northern Canada, Alaska, Great Britain, Ireland, Iceland, northern Scandinavia and Siberia.

Biology

All wasps that form obvious social colonies belong to the family Vespidae. Species of the Southeast Asian subfamily Stenogastrinae, however, live in colonies with only very small populations and a subsocial organisation.

Fig. 4.47

a Vespa crabro

b Vespula germanica

Together with the Maseridae and Eumenidae, which are largely solitary, the Vespidae are included in the superfamily Vespoidea (= Diploptera). Most members of this superfamily, apart from Stenogastrinae and most Maseridae, are able to fold their paired wings over each other while at rest. Most solitary wasps use their venomous sting to catch prey – chiefly insects or their larvae – for their own consumption or to feed their offspring. The same is also fundamentally true for the social wasps (Vespidae), who supplement their carbohydrate requirements with nectar or ripe fruit in addition. However, an important function of the venomous sting in social wasps is also defence. A cornered wasp will not hesitate to sting, and close to the nest, wasps and hornets demonstrate aggressive collective defensive behaviour towards enemies of the colony.

Polistinae: morphologically distinct from the Vespinae, in that the constricted region between the first and second segments of the abdomen (petiole; "wasp waist") connects the two segments in a gradual, flowing form, while in the latter the division between the thorax and abdomen is marked by an abrupt cleft. Polistes species form small colonies with a maximum of 150 individuals.

Vespinae: like most social wasps they build papery nests from plant fibres that they chew and then mix with saliva. Depending on the species, the nests are constructed either underground or aboveground. The lifespan of each colony is generally one year, and only the queen hibernates, to establish a new colony each spring. Vespula vulgaris form the largest colonies, with 5,000 workers or more; the colonies of most other Vespinae are considerably smaller.

Risk

See also General information on hymenopterans: Epidemiology.

Social wasps are often found in large numbers in close proximity to humans, attracted in particular by sweet drinks and food or meat products. Due to their prevalence close to humans as well as their marked defensive behaviour, the Vespinae, and to some extent the Polistinae, are virtually the only members of the Vespoidea superfamily that have any medical relevance.

Hornets (V. crabro, the European hornet), with a body length of 4–5 cm, are the largest and at the same time most feared members of the wasp family, although their stings are not significantly more serious than those of other wasps or bees. In addition, hornets have become relatively rare in Europe. The genus Vespula is the most significant for humans. In Europe this genus is represented by V. germanica (German wasp), V. vulgaris (Common wasp) and V. rufa (Red wasp) and in the USA by V. germanica, V. maculifrons (Eastern yellowjacket), V. pennsylvanica (Western yellowjacket), V. squamosa (Southern yellowjacket) und V. vulgaris. Most Vespula species build their nests underground, but V. germanica colonies are often found in buildings, attics or shutter casings. V. germanica is a common cause of hymenoptera stings. Originally native to Europe, it has now become established in various parts of the world (New World, South Africa, Australia and New Zealand).

Literature (biological)

Akre and Reed 1984, Edwards 1980, Kemper and Döhring 1967, Spradbery 1973, Brothers 1999

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