40 GENERA OF HYMEXOPTERA. 



Tliis is one of the most (lifticult and luisatisfiR-tDry laiiiilics to tabu- 

 late, hecaut^e the cliaracter:? that have been nuule known are, in many 

 cases, so prone to vary and become intermediate. For insit^ince: in 

 the long- established irenera Mc^o/rptus and Tr;jpli<>ii, the turnicr is 

 characterized chiefly by the i>ctinl:itc abdomen, and the latter by the 

 sessile abdomen, while Me--<olt'm.% an intermediate genus, is distin- 

 guished bv the subpetiolate or subsessile abdomen, the difheulty being 

 to determine wh(M-e one ends and the other begins. Of course, there 

 are other (Utierential charactei-s, such as the transverse or buccate 

 head, carinate or smooth petiole, slender or robust legs, etc., but these 

 also show the same disposition to vary, so that there are frequent 

 cases where, with our present imperfect knowledge of characters, we 

 are at a loss to say in what genus the species shoidd be placed. This 

 difhcultv. however, can be overcome by a careful study of a large 

 amount of material. 



Table of Subfamilies. 



First scfrinciit of the fleprosseil iibdoiiieii. which is in-dunciihitc. hent or curved 



towards its apex 2. 



First. segment of the a1)domen, as a nik'. straight, its si)iraeles placed at the mid- 

 (Ue. or before the middle, rarely behind the middle, in which case the 



abdomen is compressed 3. 



2. — Ovipositor hidden, or only slightly exserted ; basal half or two-thirds of first 

 abdominal segment slender, the apex generally nuich exjianded, its 

 spiracles not as closely approximate to each other as to the apex of the 

 segment; base of second segment almost always with lateral pits or de- 

 pressions (gastrocoeli) ; areolet pentangular; mesothorax generally 

 without longitudinally imiiressed lines (parapsidal grooves). 



Ichneumoninse. 

 Ovipositor distinctly exserted, rarely short as in Stilpnus; spiracles of tirst 

 abdominal segment more approximate to each other, as a rule, than to 

 the apex of the segment, which is sometimes scarcely expanded; areolet 

 pentangular, quadrate or incomplete; sometimes wingless or nearly so 

 as in Pe-omachas and allied genera; mesothorax generally with distinct 



parai)si(lal grooves; gastrocoeli subobsoleti' or wanting Cryptinse. 



:j. — Ovii)ositor short or not exserted, rarely long, as in some genera of Ophioninse. 

 Abdomen compressed throughout or only tlu' posterior hall", peliolate, 

 rarely .sessile or subse.ssile as in BitnchuK ; areoU^t triangular, rhomboido- 

 triangular, or wanting; face generally clothed with a short, dense, se- 

 riceous i)ubescence Ophioninse. 



Abdomen sometimes completely depressed and sessile as in Mctupiua, Bas^us, 

 etc., generally not entirely depressed, largest towards the apex which is 

 often subcom|ire.ssed in f, elongate, fusiform, ses.sile or petiolate, in the 

 latter case never with the areolet pentangular; areolet irregular, trian- 

 gular or wanting, rarely pentangular Tryphoninse. 



