ENEMIES OF APHIDES. 39 



tions of life are such as to render the change essential to con- 

 tinued existence. 



Passing from the consideration of the metamorphosis, we will 

 now examine the second ground on which the removal of the 

 Dragon-flies from the Neuroptera to the Orthoptera has been 

 supported. 



Mr. W. S. Dallas tells us that " one character almost univer- 

 sally holds good, and this is derived from the structure of the 

 ligula. Throughout the more highly organised Orthoptera the 

 ligula is, almost without exception, divided or cleft in front either 

 in two or four lobes, and the indications of division may even 

 continue down into the basal part of the labium, showing very 

 clearly the original construction of the whole labium from a pair 

 of organs similar to the maxillae. In the true Neuroptera, although 

 the ligula is occasionally cleft in front, the general rule is that the 

 parts of the labium are united in the middle line so closely as to 

 entirely conceal the original construction of the organ of two 

 lateral halves, so that the labium really approaches more nearly to 

 that of the Beetles than to that of the Orthoptera." 



This expresses pretty succinctly the views of those naturalists 

 who propose to break up the Neuroptera as arranged by Linnaeus, 

 and to place the most important sections with the Orthoptera. As 

 I have already pointed out, in this event the Aphis-eating Hemero- 

 biidcB and ChrysopidcB would become the typical genera of the 

 remaining Neuroptera. To arrive at a correct conclusion as to 

 the value of the structure of the labium in this group, I have 

 examined and drawn as many examples of the different species as 

 possible during the past few months, with the result that I am 

 disinclined to recognise it as of any weight as an ordinal charac- 

 ter, although as a generic feature it is a most useful guide. 



On Plates I. and II., I have reproduced my drawings with as 

 much delicacy and exactness as the lithographic process employed 

 admits, and in addition to the labia of Agrion, Ltbellula, He7nero- 

 bius, and Sialis among the Neuroptera, the reader will find the 

 same organ as found in the House Cricket (Gryllus domesticus) 

 and the Earwig ( Forficularia auricularia), as representatives of 

 the Orthoptera. 



In the labium of Sialis lutaria (PI. II., Fig. 2), which is 



