Hymenoptera (sawflies, wasps, ants, and bees) play a fundamental role in virtually all terrestrial ecosystems and are of substantial economic importance as parasitoids, predators, and pollinators. The term Hymenoptera is derived from the membrane (hymen) like wings (pteron).
DNA and fossil evidence suggest the Hymenoptera started to diversify about 280 million years ago. The early Hymenopterans (sawflies) fed on plants before some diversified to become parasites, developed the formation of a wasp waist and evolved a venomous stinger to subdue mobile hosts, then came the evolution of eusociality, and the switch from hunting prey to collecting pollen.
The Wasp Waist
Sawflies are those Hymenoptera that lack the wasp waist. The wasp waist is a constriction between the first and the second abdominal segment greatly improving the manoeuvrability of the abdomen’s rear section, including the ovipositor which is the egg-laying tube which is sometimes very long and mistaken for a stinger.
Stingers evolved in the common ancestors of stinging wasps, ants and bees about 200 million years ago. Stingers are modified ovipositors that can penetrate the skin or exoskeleton of other animals and deliver a venom; either for protection or to immobilise prey.
The most common wasps, such as German, common and paper wasps, are eusocial, living in large colonies, however, the majority of wasp species are solitary, with each adult female living and breeding independently.
Ants evolved from wasp-like ancestors about 140 million years ago; about the time that flowering plants appeared. There are very many species from ones that form very large eusocial colonies to small groups.
It is estimated that about 140 million years ago the bees split from wasps when they switched from a predatory to herbivorous lifestyle. There are many species of bees, some solitary and some forming large colonies such as the beneficial bumblebees and honey bees.
Eusociality is practised by some, but not all, wasps, ants and bees. It has the characteristics of cooperative care of offspring by other individuals, overlapping generations within a colony of adults, and a division of labour into reproductive and non-reproductive groups. Termites are also eusocial insects.
Hymenopterans are one of four mega-diverse insect orders, comprising over 150,000 described species and maybe 1 million existing, but, as yet, undescribed species.
Beneficial or Pests?
Only a few of these Hymenoptera are ever regarded as pests. Many more are our precious pollinators and beneficially parasitise the pests in our garden and on our crops.