NATURAL SCIENCES OF PHILADELPHIA. 105 



aciculate ; basal fovaj (gastrocoeli) of second segment large, deep, 

 and obliquely striated. Length G lines. 

 Orizaba. (Sumichrast, No. 121.) 



2. Fatroclus lectus. 



Ichneumon lectus, Cress., Trans. Am. Eut. Soc, ii. p. 18, % J. 



Orizaba. (Sumichrast, Xo. G.) 



3. Fatroclus toltecus. 



Ichneumon toltecus, Cress., Trans. Am. Eut. Soc, ii. p. 17, 'J, 9- 



Orizaba. (Sumichrast, No. 32 9,136 %.) The antennae of the 

 % are black, with the scape ferruginous. 



Subgenus Ichneumon. 



In this subgenus are included a large number of species vary- 

 ing greatly in form, but with such intermediation that no line to 

 divide them even into subgenera can be drawn. The head in 

 some species is large, broad, and buccate, but is gradually re- 

 duced to a small, flat, triangular form. The antennae vary from 

 robust, involute (9), with very short, almost moniliform, joints, 

 to a very slender form, not at all involute (9), with elongate 

 joints, and sometimes slightly dilated near the apex, as in Joppa. 

 The scutellum varies from being perfectly flat, through convex, 

 conical, to spinose, and even bispinose, with all intermediate 

 grades. So also with the metathorax, which varies from being 

 rounded, with no appearance of lateral protuberances, to truncate 

 behind, with long and acute lateral spines. The species having 

 the last character, together with a slender form, were formerly 

 referred to Hoplismenus ; but since the examination of so many 

 intermediate forms, it is quite impossible to draw a dividing line 

 between it and Ichneumon ; therefore, no attempt is made here 

 to divide the species into subgenera. 



The following diagnostic table will assist in determining the 

 species : 



Scutellum flat, suhconvex, or convex: 

 Body entirely honey-yellow or ferruginous : 

 Large ; scutellum flat above, lateral margin carinate, sides abrupt ; 

 metathorax without spines ; antenuoe black, with white an- 



nuUis in 9 8. dilucidus. 



Medium; scutellum-perfectly flat, sides not abrupt; metathorax Avith 

 short acute spines; antennfe, 9? tricolored, ferruginous, 



white and black 9. ablutus. 



8 



