RUDIMENTARY ORGANS 393 



is a similar eye in a functional condition, but in all other Verte- 

 brates it is wanting. In its place there is an organ whose func- 

 tion is not known but which is homologous with the pineal eye 

 of Cyclostomes and lizards, and is probably a functionless 

 rudiment. The rudimentary paired eyes of cave fishes belong 

 in the same category. 



797. As an example, from among invertebrates the wings 

 of insects may be mentioned. Most insects have wings, but 

 the order Aptera contains no winged forms. In this group 

 there are no rudimentary wings or other evidence that the 

 insects ever possessed wings. The order Hemiptera contains 



FIG. 245. Hibernia marginaria, a species of moth in which the female has 

 wings much reduced and useless. A, Male; B, female. Xi 1/2. 



many wingless forms, but many others are winged and many 

 have rudimentary wings. In this case the wingless forms are 

 regarded as representing a degenerate condition. In other 

 orders there is also evidence of degeneration of wings. The 

 male gipsy moth flies well. The female is also provided with 

 well-developed wings, but she never uses them. Among the 

 species of the geometrid moth genus, Hibernia, the females are, 

 in some cases, wholly without wings, while in others various 

 stages in the reduction of wings may be found. A similar 

 condition exists in the beetle family, Lampyridae, the common 



