64 NORTH AMERICAN BLATTIDAE 



When compared with the species of apparently nearest rela- 

 tionship, /. vilis,^'^ the present insect is found to differ as follows: 

 cf Lateral lobes of pronotum concolorous with disk, in vilis usually- 

 weakly, sometimes strongly, defined in a paler color; wings with 

 mesal marginal area of costal veins often paler than the surround- 

 •ng portions, in vilis darker; incomplete rami of ulnar vein 

 normally oblique; supra-anal plate distinctly more produced; 

 meso-distal production of subgenital plate more decided ; styles of 

 the general type found in /. morio and /. riifa, with dextral style 

 distinctly the larger and armed on dorsal surface at apex only, in 

 vilis the dextral style is very slightly the stouter, gradually taper- 

 ing, with dorsal surface, from near the base, supplied with minute, 

 chitinous spines; limbs normally unicolorous, in vilis the tibiae 

 and tarsi are normally much paler than the other portions. 



9 Interocular space narrower and very dark; tegmina subquad- 

 rate with sutural margins attingent, in vilis lateral, broadly lance- 

 olate, with sutural margins oblique to narrow, rounded apices. 



The following features are of importance in distinguishing the 

 species. 



Male. (Plummer's Island, Maryland.) Size medium large, form moderately 

 slender for the group. Interocular space slightly greater than interocellar space. 

 Ocelli large, with flat surfaces rather sharply oblique to interocellar area, as m morio. 

 Maxillary palpi rather short, fifth (distal) joint longer than third, fourth slightly 

 shorter than third joint. Tegmina with point of greatest width meso-distad ; dis- 

 coidal sectors slightly radiating, those toward the sutural margin being distinctly 

 oblique to that margin. Dorsal surface of abdomen with sixth and seventh seg- 

 ments alone specialized, showing the remarkable condition typical for the species 

 of the genus.88 Supra-anal plate margined proximad by concave distal margin of 

 preceding segment, its surface there broken by aweak, but distinct, transverse suture; 

 free margin straight and oblique laterad to mesal third which is transverse, the 

 angles thus formed blunt. In the anal orifice, beneath the base of each cercus, a 

 heavily chitinous arm is directed mesad, both tapering to their acute apices, the 

 sinistral considerably the longer and, toward the apex, curved dorso-cephalad. 



«' 1869. Ischnoptera vilis Saussure, Rev. et Mag. Zool., Ser. 2, xxi, p. 112. [ [cf ], 

 Argentine Republic] 



The above comparisons are made from the following material before us of this species. 



Sapucay, Paraguay, X to III, 2, 1902 to 1904, (W. T. Foster), iid" , [Hebard Cln. and 

 A. N. S. P.]. 



Misiones, Argentina, XII, 12, 1910 and I, 191 1, (P. Jorgensen), 2cf , [A. N. S. P.]. 



La Cumbre, Cordoba, Argentina, (C. Lizer), i d", i 9 , [A. N. S. P.]. 



** See generic description and pi. II, fig. 12. 



