No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 65 



so that the head and tail ends nearly meet. Embryonic de- 

 velopment is completed in a day, and the larva must pass 

 through a complex metamorphosis to reach the imaginal state. 



The chasm between these two extremes is bridged by the 

 less metabolic insects (Coleoptera, Neuropotera, Lepidoptera, 

 Hymenoptera, etc.). The quantity of yolk is intermediate be- 

 tween that of the Orthopteran and Dipteran ^g^. The germ- 

 band, like that of the Muscidae, is longer than the Qgg when it 

 reaches its full length. But it is at this time much narrower 

 than the yolk-mass, whereas in the Muscidae it embraces nearly 

 half the circumference of the yolk. The larvae usually hatch 

 after a period of ten to thirty days in a relatively more ad- 

 vanced stage of organization than Dipteran larvas. 



It is probable that the quality of the yolk is also an impor- 

 tant factor in development. The yolk of the Orthoptera and 

 Rhynchota is dense and resembles that of the crustacean and 

 Arachnid Qgv^ while the yolk of the Metabola seems to have a 

 much looser molecular structure. Hence, bulk alone is no 

 criterion of the amount of yolk in an insect's ^gg. 



The view here advocated, that the eggs of the Ametabola 

 contain more yolk than those of the Metabola, admits of some 

 exceptions. Thus the 17-year locust {Cicada septendecim) 

 is a large insect with incomplete metamorphosis, but it never- 

 theless produces a great number of very small eggs. This is, 

 however, seen to be a greater advantage to the insect than the 

 production of a few large eggs, when we consider the extremely 

 long period of larval life and the vicissitudes to which the 

 larvae may be subjected during all this time. Similarly, Meloe 

 aiigiisticollis produces a great number of very small eggs, while 

 the eggs of the smaller beetles {DorypJiora, e.g.) are much 

 larger. But Mcloe is a parasite form, and probably only a few 

 of its many offspring ever succeed in gaining access to the eggs 

 of the bee. The larvae, as shown by their hypermetamorpho- 

 sis, are subjected to very varied conditions, and this would still 

 further tend to reduce the number of successful individuals. 

 As in anemophilous plants many germs are produced, but very 

 few are destined ever to prosper. Many other exceptions to 

 the general rule, like these two, are probably due to habits 



