Wasp Adult
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant.
Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their numbers, or natural biocontrol. Parasitic wasps are increasingly used in agricultural pest control as they prey mostly on pest insects and have little impact on crops.
The majority of wasp species (well over 100,000 species) are "parasitic" (technically known as parasitoids), and the ovipositor is used simply to lay eggs, often directly into the body of the host. The most familiar wasps belong to Aculeata, a division of Apocrita, whose ovipositors are adapted into a venomous sting, though a great many aculeate species do not sting. Aculeata also contains ants and bees, and many wasps are commonly mistaken for bees, and vice-versa. In a similar respect, insects called "velvet ants" (the family Mutillidae) are technically wasps.
Wasp Larva
The suborder Symphyta, known commonly as sawflies, differ from members of Apocrita by lacking a sting, and having a broader connection between the mesosoma and metasoma. In addition to this, Symphyta larvae are mostly herbivorous and "caterpillarlike", whereas those of Apocrita are largely predatory or parasitoids.
While the vast majority of wasps play no role in pollination, a few species can effectively transport pollen and therefore contribute for the pollination of several plant species, being potential or even efficient pollinators in a few cases such as figs pollinated by fig wasps, they are the only pollinators, and thus they are crucial to the survival of their host plants.
Anatomically, there is a great deal of variation between different types of wasp. Like all insects, wasps have a hard exoskeleton covering their three main body parts. These parts are known as the head, mesosoma and metasoma. Wasps also have a constricted region joining the first and second segments of the abdomen (the first segment is part of the mesosoma, the second is part of the metasoma) known as the petiole. Like all insects, wasps have three sets of two legs. In addition to their compound eyes, wasps also have several simple eyes known as ocelli. These are typically arranged in a triangular formation just forward of an area of the head known as the vertex.
It is possible to distinguish between sexes of some wasp species based on the number of divisions on their antennae. Male yellowjacket wasps, for example, have 13 divisions per antenna, while females have 12. Males can in some cases be differentiated from females by virtue of having an additional visible segment in the metasoma. The difference between sterile female worker wasps and queens also varies between species but generally the queen is noticeably larger than both males and other females.