46 THE CLASS OF INSECTS. 



Mr. Dunning describes a specimen of Fidonia piniaria, 

 "which was sexually a female, and the abdomen was appar- 

 ently distended with eggs ; the general color was midway be- 

 tween the colors of the ordinary male and female, but the size 

 and markings were those of the male. (Transactions Ento- 

 mological Society, London, Aug. 7, 1865.) Professor West- 

 wood states that "he had an Orange-tip Butterfly (Anthocharis 

 cardamines) , which was female in every respect, except that 

 on the tip of one fore- wing were about a dozen of the bright 

 orange scales which characterize the male." 



THE EGG. Professor H. J. Clark (Mind in Nature) defines 

 an egg to be a globule surrounded by the vitelline membrane, 

 or yelk-envelope, which is protected by the chorion, or egg- 

 shell, consisting of "two kinds of fluid, albumen and o7, which 

 are always situated at opposite sides or poles." "In the earli- 

 est stages of all eggs, these two poles shade off into each 

 other," but in the perfectly developed egg the small, or albu- 

 minous pole, is surrounded by a membrane, and forms the 

 Purkinjean (germinal) vesicle ; and thirdly and last, the inner- 

 most of the three globules is developed. This last is the 

 Wagnerian vesicle, or germinal dot. The oily matter forms the 

 yolk. Thus formed, the egg is the initial animal. It becomes 

 an animal after contact with the male germs (unless the product 

 of organic reproduction), and the egg-shell or chorion is to be 

 considered as a protection to the animal, and is thrown off 

 when the embryo is hatched, just as the larva throws off its 

 skin to transform into the pupa. So that the egg-state is 

 equivalent to the larva state, and hence there are four stages 

 in the life of an insect, i. e. the egg, the larva, the pupa, and 

 the imago, or adult state. 



The egg is not always laid as a perfect egg (Clark). It 

 sometimes, as in the Ants, continues to grow after it is laid by 

 the parent, like those of frogs, which, according to Clark, "Are 

 laid before they can hardly be said to have become fully formed 

 as eggs." Again, others are laid some time after the embryo 

 has begun to form ; and in some, such as Melophagus and 

 'Braula, the larva is fully formed before it is expelled from the 

 oviduct. 



