THE HEXAPODA OR TRUE INSECTS
There are a number of Hexapoda, or true insects, which are, in one way or another, poisonous to man. These belong primarily to the orders Hemiptera, or true bugs; Lepidoptera, or butterflies and moths (larval forms); Diptera, or flies; Coleoptera, or beetles; and Hymenoptera, or ants, bees, and wasps. There are various ways in which they may be poisonous.
1. Piercing or biting forms may inject an irritating or poisonous saliva into the wound caused by their mouth-parts.
2. Stinging forms may inject a poison, from glands at the caudal end of the abdomen, into wounds produced by a specially modified ovipositer, the sting.
3. Nettling properties may be possessed by the hairs of the insect.
4. Vescicating, or poisonous blood plasma, or body fluids are known to exist in a large number of species and may, under exceptional circumstances, affect man.
For convenience of discussion, we shall consider poisonous insects under these various headings. In this, as in the preceding discussion, no attempt will be made to give an exhaustive list of the poisonous forms. Typical instances will be selected and these will be chosen largely from North American species.
PIERCING OR BITING INSECTS POISONOUS TO MAN
Hemiptera
Several families of the true bugs include forms which, while normally inoffensive, are capable of inflicting painful wounds on man. In these, as in all of the Hemiptera, the mouth-parts are modified to form an organ for piercing and sucking. This is well shown by the accompanying illustration ([fig. 16]).