ARTICULATA. 133 



{pi. 81, figs. 18, 23, 43, &c.). The inaccuracj of this will appear, upon 

 reflecting that the thorax in the IIymeno2>tera bears the wings and all the 

 feet, w^hilst the segment next to the head in the Coleoptera bears the anterior 

 pair of feet alone, corresponding oulj to one third the thorax of the former. 

 In the Coleoptera, the elytra or wing-covers, when in a state of repose, 

 generally cover the abdomen and two thirds of the thorax, keeping the 

 latter out of view when the insect is viewed from above. A lateral or 

 ventral view {pi. 81, figs. 105, 106, 130) will exhibit the remaining parts 

 of the thorax bearing the wings and the medial and posterior feet. In some 

 cases the abdomen is eiltirely exposed, the elytra being so short as not to 

 extend beyond the thorax {pi. ^1., figs. 1-7). The three segments which 

 comprise the thorax both of a hymenopter and a coleopter., may be recog- 

 nised by the three pairs of feet ; but whilst that next to the head (named 

 the prothorax) is conspicuous in the latter, it is reduced to a mere collar in 

 the hymenopter, where the next segment or mesothorax is largely developed, 

 to bear the large anterior pair of wings, whilst the corresponding part in 

 the Coleoptera have to bear the elytra, w^hich are not used as organs of 

 flight. Finally, the metathorax, or third segment of the thorax, is reduced 

 in the Hymenoptera, the wings of this segment being small and of but 

 secondary importance in flight, whilst in the Coleoptera the same organs 

 are the only instruments of flight. 



Most insects are ovi^iarous; some, as Musca carnaria., are ovo-viviparous, 

 the eggs being hatched within the body, and in the Pupipara the young 

 advances to the pupa state before it is excluded, the apparent egg-shell being 

 the pupa case. 



The egg of insects is generally oval, but there are many other forms, as 

 globular, hemispherical, cylindrical, lenticular, conical, pyriform, &c. The 

 eggs of Ilemerobius are attached to leaves at the extremity of a long thread. 

 Some are crowned at one extremity, and others have ear-like appendages. 

 In most cases the surface is smooth, but they sometimes occur ribbed or 

 sculptured in various patterns. White, yellow, and green, are almost the 

 only colors observed in them. The eggs of insects are deposited according 

 to the wants of the young to which they are to give birth, either in earth, 

 water, dung, upon dead animals, or in putrid vegetables, beneath the skin 

 of caterpillars, in punctures in living vegetables, where they sometimes 

 cause galls ; some are glued to leaves or branches, and others are placed in 

 cells where the young are fed. 



The larva appears when the shell of the egg is burst at the period of its 

 maturity. The name larva is applicable to the young of all insects, although 

 those of butterflies are also named caterpillars., and those of certain flies 

 maggots. The larva is in most cases unlike the adult insect, generally 

 appearing as a cylindrical worm, either without feet or with six or more 

 walking organs, of which six only are articulated feet. In this condition 

 nourishment is taken, often in great quantities ; the growth is rapid, and a 

 series of moultings is undergone. When the larva has attained its full size, 

 in many cases it becomes an inactive pupa without external organs, and 

 incapable of locomotion or taking food ; but when the pupa case is burst, the 



ICOXOGRAPHIC ENCYCLOPAEDIA. — VOL. II. 22 337 



