One of the larger orders of insects, comprising the sawflies, wasps, bees, and ants. The name comes from the membranous wings, of which most forms have two pairs, the front wings larger than the back. Females typically have a special ovipositor for inserting into hosts or otherwise inaccessible places, often modified into a stinger. The young develop through complete metamorphosis - that is, they have a worm-like larval stage and an inactive pupal stage before they mature.
Among the hymenopterans gender is determined by the number of chromosomes the individual receives. Fertilized eggs get two X chromosomes, the Y chromosomes being non-existent, and so develop into diploid females; unfertilized eggs only receive one, and so develop into haploid males. Because of this, females on average actually have more genes in common with their siblings than they do with their own offspring. Because of this, cooperation among kindred is unusually advantageous, and varying degrees of sociality have appeared several times among the different subgroups. The most extreme form is eusociality, where a colony has a majority of sterile females called workers who care for one or more reproductive queens.
The wasps, bees, and ants together make up a suborder of the Hymenoptera called the Apocrita, characterized by a constriction between the first and second abdominal segments called a wasp-waist. The remaining forms (sawflies) were once classified as a second suborder, the Symphyla, but this appears to be paraphyletic. A classification of the Apocrita is as follows:
- Vespoidea (yellowjackets, ants, etc)
- Apoidea (bees)