SFjRING tails. 401 



CASE 



^^i- Order THYSANURA, Latr. (Spring tails). 



This order of insects is certainly not in its natural position here. 

 We do not pretend that it is ; but unless we were to abandon the 

 great convenience of bringing all the Apterous insects into one 

 group, we do not see where else we could put them. Their 

 natural position is between the Crustacea and the Neuroptera 

 (the lace-winged flies). Some entomologists place them among 

 the Neuroptera, some among the Orthoptera, but this seems to us 

 a stretch of arbitrary power, even worse than putting them here. 

 Perhaps we should have begun with them, but they would have lain 

 like an isolated lump as much at the beginning as here, leading 

 to nothing, and would have interfered with the natural transition 

 from the Isopodous crustaceans to the Myriapods ; and Sir John 

 Lubbock's interesting discovery of the genus Pauropus, which 

 seems at once to connect the Myriapods with the Thysanura, and 

 both with the Crustaceans, seems to warrant us at least in bringing 

 this group into the Aptera. The reader, therefore, will regard 

 their interpolation here as one of the digressions that we have 

 more than once been forced to adopt as a choice of difficulties. 



We do not say that it would not be more philosophical to do 

 away with the Aptera as a distinct division altogether, and to 

 have carried the Pediculi to the Hemiptera, the Thysanura to the 

 Neuroptera or Orthoptera, and treated the remaining groups not 

 as Aptera, but simply as Arachnids and Myriapods; but the 

 course we have taken has its conveniences, and its adoption does 

 not in any way interfere with the proper understanding of the 

 different groups, or put any obstacles in the way of studying 

 them. 



Until 1873, this order was always regarded as a single group, 

 sufficiently homogeneous. Sir John Lubbock, however, in that 

 year published an able and exhaustive monograph of them, and 

 gave it as the result of his researches that there was so much 

 difference between two parts of it that they could not be included 



