SPRING-TAILS 



191 



Fig. 97, 

 tube : 



Corynothrix horealis : a, ventral 

 b, the spring. (After Tullberg.) 



The peculiar shape of the members of the Smynthuridae is 

 sufficient for their identification. They possess a very convex 

 abdomen, and very near to it 

 a large head, the intervening 

 chink being occupied by the 

 small thorax. The segmenta- 

 tion of the body is not easily 

 distinguished. Nicolet states 

 that the thorax consists of 

 three segments and the abdo- 

 men of the same number, and 

 that when the Insect emerges 

 from the egg these divisions 

 can be perceived. In after life the posterior part of the thorax 

 becomes amalgamated with the abdomen, so that it is difficult to 

 trace the divisions, but there appears to be no information as to 

 the manner in which this change occurs. 

 Some of these minute Insects frequent 

 trees and bushes, and their leaping powers 

 are very perfect, so that it is difficult to 

 capture them. The family includes both 

 the Smynthuridae and the Papiriidae of 

 Lubbock. 



The two most characteristic organs of 

 the CoUembola are the spring and the 

 ventral tube. The first of these is an 

 elongate structure attached to the under- 

 side of the abdomen near its extremity, 

 either on the penultimate or ante-penulti- 

 mate segment. It consists of a basal 

 part, and of two appendages attached 

 thereto. It is carried under the Insect 

 bent forwards, and is retained in this 

 position by means of a catch which pro- 

 jects from the under surface of the third 

 segment of the body, descending between 

 the two branches of the spring, and pass- 

 ing under the extremity of its basal seg- 

 It is considered that the spring is elastic, is flexed under 



Fig. 98. Sviynthurus varie 

 gatus, with spring ex 

 tended. (After Tullberg. 



ment. 



the body by muscular action, and, being retained in this position 



