174 I August, 



HELP-NOTES TOWARDS THE DETERMINATION OF BRITISH 

 TENTHREDINID.E, &c. (10). 



BY THE KEY. P. D. MORICE, IM.A., T.-P.E.S. 



"We come now to what in Konow's system forms Tribe 1 of the 

 Tenthredinini, viz., the NemaUdes. 



These insects are divided by Thomson, entirely on neuration 

 characters, into two short genera, Cladius and Leptocercus, and one 

 exceedinf^ly long one, Nematus, the latter including over 100 species, 

 and the former two together only 11. Konow, on the other hand, 

 recognises no less than 17 distinct genera of Nevuitides, 12 of which 

 represent Thomson's one long genus Nemaiiis. Yet these two classi- 

 fications are by no means so different as might be supposed ; for 

 Thomson in describing the species of his genus arranges them in a 

 number of subsections, which, though ho docs not give them separate 

 names, agree on the whole pretty closely with the groups which 

 Konow has preferred to treat as separate genera, and are distinguished 

 in the main by the same characters. What Konow, in short, has done 

 is not to upset Thomson's classification as a whole, but to revise care- 

 fully the groups established by the elder author, occasionally altering 

 the position of species wliicii appear to him wrongly placed, and then 

 to raise these revised groups from the rank of unnamed sections to 

 that of named genera. By this, it seems to me, while substantially 

 retaining Thomson's system, he has made it a more convenient 

 instrument for arriving at specific determinations, for it is surely much 

 easier to connect in one's mind a certain collection of characters with 

 a definite name like Ilolcocneme, than with a long sti'ing of figures 

 and letters like " Sect. IV, B, aa, bb, cc, m, n, o." 



In the following tabulation I have tried to show roughly how far 

 the two classifications agree and differ. I say '" roughly," because I 

 am not quite sure as to the identity of a few of Thomson's species, 

 though his diagnoses ai'e generally so clear, that I hope I have not 

 often gone wrong over them. I cannot introduce into this table a 

 comparison of these groups with those adopted by Mr. Cameron in 

 Vol. II of his Monograph, for the latter are founded on quite a dif- 

 ferent set of characters (the colour of the ^ $ in each species), and 

 naturally lead to results which are wholly out of relation to those of 

 Thomson's structural divisions. I may say, however, that, in dividing 

 the NemaUdes into genera, Mr. Cameron has taken a somewhat inter- 

 mediate and, so to speak, "eclectic" course. He retains Thomson's 



