PERIPATUS, MYRIAPODS, AND INSECTS. 



183 



Chapter V., which treats of the Development of Insects, is 

 most interesting. Although eggs are laid by the great majority of 

 insects, a few species nevertheless increase their numbers by the 

 production of living young, in a shape more or less closely similar 

 to that of the parent. This is well known to take place in the 

 Aphididas, or green-fly insects, whose rapid increase in numbers is 

 such a plague to the farmer and gardener. These and some 

 other cases only emphasise the fact that insectsv.are preeminently 

 oviparous. In illustration of this chapter we have chosen Fig. 14, 

 which represents the larva and pupa of a bee. It will be seen 

 that the difference between the two forms a very great contrast, 

 while the further change that will be required to complete the 

 perfect Insect is but slight. When the last skin of a bee or a 



Fig. 13. — Diagram of arrangement of some of the Internal Organs of an Insect. 

 a. Mouth ; b, Mandible ; c, Pharynx ; d, CEsophagus ; e, Salivary glands 

 (usually extending further backwards) ;/, Eye ; g, Supra-oesophageal ganglion ; 

 h, Sub-oesophageal ganglion ; i, Tentorsum ; J, Aorta ; ki, k2, Z'3, Entothorax; 

 li to /8, Ventral nervous ganglion ; tn. Crop ; «, Proventriculus ; 0, Stomach ; 

 /, Malpighian tubes ; q, Small intestine ; r, Large intestine ; s, Heart ; 

 t, Pericardial septum ; ti, u. Ovary composed of four egg-tubes ; v, Oviduct ; 

 w, Spermatheca (or an accessory gland) ; x, Retractile ovipositor ; y, Cercus ; 

 z, Labrum, 



beetle is thrown off, it is, in fact, the imago that is revealed. The 

 form thus displayed, though colourless and soft, is that of the 

 perfect insect ; what remains to be done is a little shrinking of 

 some parts and expansion of others, the development of the 

 colour, and the hardening of certain parts. The colour appears 

 quite gradually and in regular course, the eyes being usually the 



