30 [February, 



UELP-NOTES TOWARDS THE DETERMINATION OF BRITISH 

 TENTHREDINID.E, &c. (12). 



BY TUE EEV. F. D. MORICE, M.A., F.E.S. 



{Continued from Vol. XL, p. 248). 



NEMATIDES (continuedj ; MICRONEMATUS, CRYFTOCAMPUS, 

 CRCESUS, HOLCOCNEME. 



In my last paper (November, 1904) I defined the normal Genera 

 of Nematides as those in which {a) the humeral cell is petiolate, and 

 (fi) the intercostal nerve strikes the subcosta distinctly before the 

 point at which the latter receives the cubitus. Of these normal 

 Genera Cameron admits three, viz., Crossus, with three British species, 

 JEuura, with live, and Nematus., with no less than 107. Thomson 

 treats the whole of them (and also Dineura) as subdivisions of his 

 enormous genus Nematus ; while Konow revises Thomson's sub- 

 divisions in certain cases, but on the whole accepts them and erects 

 them into Genera, thus breaking up the whole unwieldy mass into 

 eleven genera of manageable extent, and distinguished by real 

 (though minute) differences of structure and to some extent by their 

 general " facies," viz., Gryptocampus, Htg., Pontania, Costa, Pteronus, 

 Jur., Amauronemattts, Knw., Croesus, Leach, Holcocneme, Knw., 

 Nematus, Jur., P achy nematus, Knw., Lygcsonematus, Knw., Pristiphora, 

 Latr., and Micronematus, Knw. 



Three of these genera can usually be separated from the rest on 

 a single character. Thus, Cryptocami^us (= Euura, C.) lacks the 

 second cubital nerve, so that the 2nd and 3rd cubital cells are confluent, 

 and form one exceedingly elongate area. The same condition, how- 

 ever, may occur in abnormal specimens of almost any genus. And a 

 beginner must beware of confusing the absence of a second cubital n. 

 with the absence of 2. first (as often in Pristiphora). In both cases 

 the result is three cubital cells instead of four ; but the proportions of 

 the three cells to one another are utterly different in the two cases. 



CroesiLS, and its close ally Holcocneme, are separated by a much 

 more satisfactory difference — the structure of their hind legs. In 

 Holcocneme these have the tibias and tarsi considerably dilated and 

 flattened, or rather hollowed out, from base to apex, and in Croesus 

 the same character is carried to a paradoxical extent ; while in all the 

 other genera the leg- joints are parallel-sided, slender, and cylindrical. 

 (See fig. 10). Exactly similar differences exist, of course, among the 

 Aculeates {e. g.. Apis, Halictus, Vespa, &c.). 



