44^ TRANSFORMATIONS OF INSECTS. 



The editors of the American Natural History Miscella7iy, 1869, 

 state that the six-footed young one has enormous legs, and that 

 the head is separated from the hind body. The young tick has 

 terrible jaws, with which it buries its head and fore-part of the 

 body within the tissues of the deer. The perfect tick has eight 

 legs, which are short, and a large body. 



When considering the strong structural relation between the 

 spiders and true insects, the history of the development of the first 

 mentioned creatures within the egg and that of the metamorphoses 

 of the tracheary order should never be forgotten. The early con- ■ 

 dition of the spider within the egg has a strong resemblance to 

 that of the insect, for the head is not then forced into the chest, 

 and there are traces of segments on the body ; moreover, the six- 

 legged condition of the water mites and some ticks in their larva 

 condition refers back, like the other facts, to a common ancestry 

 with the Insecta. 



The water mites, although they rarely care to quit the depths 

 of the streams and ponds, do so at their pleasure, and run over 

 the surface, and it is evident that they are not so perfectly 

 adapted for aquatic life as many insects. Their tracheae are 

 not arranged as branchiae, and this consideration, amongst many 

 others, leads to the belief that their present mode of life was not 

 original. In a note to the admirable article by Audouin in the 

 " Encyclopedia of Anatomy and Physiology," Dr. Todd writes : — 

 " Mr. Blackwell has related an accidental discovery of the power 

 of some spiders to abstract respirable air from water. Several 

 individuals have preserved an active state of existence under 

 water for six, fourteen, or twenty-eight days, spinning their lines 

 and exercising their functions as if in air, while others have not 

 survived a single hour." 



The case of the water spider, Argyro7ieta aquatica, whose diving- 

 bell shaped nests under water, and whose method of carrying down 

 air to fill them with, are so well known and so constantly referred 

 to in all the books on natural history, loses much of its strangeness 

 and uniqueness when the above-mentioned facts are considered. 

 It does not undergo a metamorphosis, however, so that there is no 

 necessary connection between an amphibious -^;'<7^//;/zV/rt« existence 

 and a sequence of the larval, nymph, and adult condition. 



