And into the division with sucking mouths:—
Lepidoptera, or butterflies and moths; Diptera or flies, gnats, etc.; Hemiptera, or bugs, including the plant-lice, etc.
These divisions, however, have not been found to be very satisfactory, although very simple when dealing only with the perfect insect stage. In the first place, being framed on this stage only, they are not always applicable to the earlier phases of the insect's life—for instance, although a butterfly or moth has a sucking proboscis, their caterpillars have strong biting jaws, as any gardener well knows. Also bees, wasps, etc., rather upset the arrangement, as they have not only a sucking mouth but also strong biting jaws.
This system of classification has therefore been discarded by most entomologists in favour of that based on the difference between those insects which pass through the distinctive stages of caterpillar and chrysalis on the one hand, and those which emerge from the egg as diminutive likenesses of their parents on the other. In this arrangement, the Coleoptera, Hymenoptera, Lepidoptera, Diptera and Neuroptera, fall into the
first division, or Heteromorphæ as they are called; and the Hemiptera and Orthoptera into the second or Homomorphæ. The dragonflies are the only slightly discordant elements in this arrangement, as, although their larvæ have six legs and walk about under the water and never assume an actual chrysalis condition, still they can hardly be said to resemble their gorgeously coloured parents which fly about so majestically over our ponds, etc.; still this is only one of the many cases which show that nature cannot be held down by any of the arbitrary rules we make for her classification.
The Hymenoptera are therefore characterized and distinguished from other insects by having both a biting and sucking mouth, four clear wings, and by passing through the distinctive liveries of caterpillar or grub, and chrysalis or nymph. It is with this order only with which we have been dealing. To distinguish the aculeate section from the many other forms of the Hymenoptera is too complex a task to undertake here, but the presence of a narrow waist between the thorax and the body, the number of joints in the antennæ never exceeding thirteen in
the male, twelve in the female, and the presence of a sting capable of ejecting poison in this latter sex, are the most prominent features by which the aculeates may be recognized.