8 COLLEMBOLA OF MINNESOTA 



mncosity, assists the insect when travelling over a smooth, pol- 

 ished surface, as glass, for instance. To be sure, the feet are 

 not adapted to smooth surfaces. But what smooth surfaces are 

 there where these insects live? 



The second abdominal segment bears the tenaculum, catch 

 or halthaken, as it is called by various authors. Although several 

 of the best writers mention it as a character of prime impor- 

 tance in clasification, yet I think few have been able to use it 

 to advantage. It probably represents one of the pairs of prim- 

 itive jointed abdominal appendages, their basal portions fused 

 to each other and their second (terminal) parts turned laterad 

 so as to form a sort of catch to hold the spring in place when 

 not in use. Short notches or teeth serve the better to retain 

 their hold upon the furcula, which is so placed as to extend a 

 ramus (dentes) on either side of and close to the tenaculum, 

 whose two blades extend below them, holding them in position. 



The fourth abdominal segment, or sometimes the fifth, 

 bears what is variously called the furcula, saltatory organ, spring, 

 springgabel, tail, caudal appendage, etc. It undoubtedly rep- 

 resents a pair of jointed appendages. Dr. A. S. Packard com- 

 pares the ovipositor of some Neuroptera (Panorpa and Bittacus) 

 to "the leaping ovipositor of the Podura and its allies." In 

 speaking of Westwood's description of the winter neuropter, 

 Boreus, he says: "In this description we are reminded of the 

 Spring-tails (Podura) which leap by means of the long ovipos- 

 itor, and corresponding male organs, bent beneath the body." 

 I feel inclined to question this statement of the furcula being even 

 primitively an ovipositor. Evidence gained by a comparison 

 with the thysanuran genus Machilis would certainly seem to 

 deny it. Machilis has a sort of primitive furcula, as well as a 

 long, well-developed ovipositor. When at rest, the furcula is 

 carried beneath the body, its muscles continually at tension, 

 and ready for a leap when the tension on the blades of the ten- 

 aculum is loosened so as to release the furcula. The powerful 

 muscles of the furcula are balanced by the less powerful muscles 

 of the tenaculum, on account of the shorter leverage of the latter. 

 The final abdominal segment, the sixth, often bears anal horns 

 in the Poduridse and Aphoruridas. The anus is terminal, and 

 the genital papilla opens on the ventral side of the preceding 

 segment. 



