172 OTHER DENIZENS OF THE WOODS 



fcures are more or less welded together, aborted, or otherwise modified. The thorax 

 adjoins the head, and consists of three segments — prothorax, mesothorax, and 

 metathorax. Most insects have one or two pairs of wings attached to the 

 thorax, the mesothorax carrying the first pair, and the metathorax the second or 

 hind pair, which are so small in the case of the flies as to be represented 

 only by two knobs known as balancers. Wings play an important part in the 

 classification of insects, as they differ so greatly in shape, size, and formation. 

 Like the wings, the six legs of insects are attached to the thorax, namely, one 

 pair to each segment. These are also of importance in classification ; and, when 

 fully developed, consist of five segments, generally terminating in a couple of 

 claws. The legs are often wanting in the larvae, although some larvae have thick, 

 fleshy, rudimentary abdominal legs. The division of the body into three principal 

 parts is rarely so clearly discernible in the larva as in the mature insect, the 

 hinder portion of which is always formed by a limbless abdomen, consisting of from 

 four to nine, mostly nine, more or less closely connected segments. 



Insects are of separate sexes, and mostly lay eggs, although some give birth 

 to living larvae, and a few even to pupae. Moreover, in addition to fertile males 

 and females, between which there may be structural differences, neuters, or 

 imperfectly developed males and females, also occur; and many insects are 

 reproduced by the process known as parthenogenesis, while some are capable of 

 propagating even as larvae. Most, insects multiply very rapidly; many take 

 particular care of their offspring. 



As a rule, the increase of insects is only slightly controlled by their many 

 enemies, among which birds hold perhaps the first place. Still most kinds seldom, 

 if ever, attain such numbers as to disturb the balance of life. Of course, where 

 a number of certain kinds of plants are grown that are exposed to the attacks 

 of insects, as, for example, in woods, fields, and gardens, insects find suitable 

 food in great quantities and often multiply to such an extent as to do serious 

 damage. In many cases, however, the enormous increase of certain species 

 of insects is succeeded by a similarly extensive multiplication or aggregation of 

 their enemies, and disease often kills off many of the insects that appear in 

 great numbers. Whilst there is a considerable number of the so-called noxious 

 and troublesome insects, among which may be classed many parasites of man and 

 domesticated animals, the insects usually classed as useful are much less numerous. 

 It must not be overlooked, however, that most flowering plants bear seed only when 

 insects convey the pollen from flower to flower. There is no insect which has 

 not some clearly allotted place in the economy of nature ; many serve as food to 

 other animals, in the larvae of many those of others live, many kinds destroy 

 putrefying matter, and not a few devour sickly and therefore useless plants. 



Among the various orders of insects the beetles, or Coleoptera, are distin- 

 guished by possessing fore-wings and hind-wings of different structure, the horny 

 fore-wings, called elytra, covering, when at rest, the hind-wings by which the flight 

 is performed, these hind-wings being wanting in certain so-called wingless beetles, 

 whose wing-covers are for the most part aborted. Beetles are seldom many-eyed, 

 and nearly always have mouths adapted for biting. According to the number of 



