312 ZOOLOGY 



we know that these creatures are insects and Hemip- 

 tera ? We judge by the totality of their characters, 

 and especially by the young stages, which repeat more 

 or less the characters of their remote ancestors. In 

 spite of their extraordinary character, there is no doubt 

 whatever about their place in the classification. They 

 are very instructive as examples of evolution by the 

 loss of characters, accompanying a sedentary and more 

 or less parasitic existence. The loss of wings finds its 

 parallel in the lice and bedbugs, which are of course 

 wingless in both sexes. In the different species of 

 coccids there are all the stages between well-formed 

 legs and antennae, and none. In some the adult females 

 are mere bags of eggs, and to classify them accurately 

 Sexual ' we are obliged to examine the larvae. The Coccidae 

 also illustrate in a very remarkable way sexual dimor- 

 phism. The two sexes of the San Jose scale, if examined 

 by one unfamiliar with the group, might well be placed 

 in different orders of insects, the female immobile 

 and without legs, antennae, or wings, but with a highly 

 developed mouth ; the male of an entirely different 

 shape, with legs and antennae, a pair of large wings, 

 and no mouth whatever ! It is amazing that the germ 

 cells of this species should be able to produce such 

 totally different organisms. We are led to think of 

 the possibilities inherent in living beings, but perhaps 

 sometimes never realized. There is one species, the 

 mussel scale of the apple, which reproduces partheno- 

 genetically and only very rarely produces males. 

 Suppose that all coccids developed this characteristic, 

 and no males were ever produced ; who could ever 

 guess that locked up in the germ cells of the female was 

 the potentiality of a being unlike her in almost every 

 respect ! 



