Ants, Bees, Parasitoid Wasps, Sawflies, Wasps
The Hymenoptera comprise a significant proportion of the insect diversity in most terrestrial habitats. They are one of the four mega-diverse orders of insects, along with the Coleoptera (beetles), Diptera (flies), and Lepidoptera (moths and butterflies). There are over 150,000 species described world-wide of which approximately 10% are described from Australia. However, the true size of the order is likely to be more than five times this number.
The order includes all those insects that are commonly known as wasps, ants, bees, parasitoid wasps and sawflies, It is normally divided into two suborders: the Symphyta (sawflies) and the Apocrita (comprising all other groups). The Symphyta is paraphyletic (not a natural group in an evolutionary sense), is largely found in the northern hemisphere, and is represented in Australia by only six of 14 families (of which the Siricidae is introduced) and less than 200 species, most of which belong to the Pergidae. The monophyletic Apocrita makes up the vast majority of hymenopteran species, and comprise 63 families in Australia, of which three families, Austrocynipidae, Austroniidae and Peradeniidae, are endemic to the region. Apocritan wasps differ markedly in their morphology from the Symphyta in that they have a pronounced constriction or waist between the first and second abdominal segments which clearly divides the apparent thorax from the rest of the abdomen.
The Australian Hymenoptera are extremely rich in species, particularly the ants (Formicidae), bees (comprising five families), wasps belonging to the families Crabronidae, Mutillidae, Pompilidae, Tiphiidae and Vespidae, and the parasitoid superfamilies Chalcidoidea, Ichneumonoidea and Platygastroidea. The superfamily Cynipoidea is noticeably depauparate in Australasia compared with the northern hemisphere where they are a common group of gall formers on plants. However, in Australasia this niche appears to be largely taken over by members of the Chalcidoidea.
The parasitoid superfamilies are by far the largest in terms of species but overall they are also the poorest studied. They oviposit their eggs into or onto the juvenile stages of other insects (as well as other arthropods such as spiders), and the parasitoid larva then feeds on the host to complete its development. This aspect of the biology of parasitoid wasps, in conjunction with them often being host specific, has rendered them ideal as biological control agents of a large range of agricultural and horticultural pests.
There have been a number of significant changes to the classification of the Hymenoptera in the last 20 years that have resulted from phylogenetic analyses using either morphology or DNA sequence data, or both. The classification adopted here only includes superfamilies and families, and has not used the traditional suborder classification given that Symphyta is paraphyletic. The bees which have previously been treated as 1-11 separate families, are the most problematic as there is strong phylogenetic evidence that they have evolved from within the Sphecoidea. To maintain some stability to the family level classification within the Apoidea s.l. the scheme of Michener (2000) is adopted here for the bees, along with the informal group names Spheciformes and Apiformes.
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