362 PROCEEDINGS OP THE ACADEMY OP 



black spot, and an oblique whitish line on each side near the eyes ; nasus ob- 

 scurely lineated with fuscous; antennae fuscous. Thorax fuscous, with whitish 

 sutures. Legs pale, with knees aod tarsi fuscous. Wings hyaline ; an irregular 

 band en the apical margin, connected with the pterostigina by about four irreg- 

 ular spots, an irregular median band attaining the costa, and the base of the 

 costa, fuscous ; veins black, except the posterior side of the discoidal cellule, 

 and a small spot at the furcation of the 1st sector, which are white ; pterostigma 

 fuscous at tip, at base hyaline ; posterior wings hyaline, with violaceous re- 

 flections. 



Length to tip of wings 4 mill. Captured one specimen in South Illinois. 



Psocus amabilis, n. sp. Head dull luteous, immaculate ; antennae robust, 

 pubescent, fuscous, with two basal joints and the base of joint9 3 6 pale. 

 Thorax and legs dull luteous, the tarsi a little fuscous. Wings hyaline, with a 

 black spot on the middle of the posterior margin ; pterostigma hyaline, truncate 

 at tip, with a black spot at its base ; veins black, except the discal bifurcation, 

 which is white. This bifurcation is not angular, as in all the above species, 

 but rounded and peduncled, as in the species figured in Westwood's Introduc- 

 tion (ii. p. 18, fig. 8); from which, however, this species differs by its two- 

 jointed feet, closed discoidal cellule, and the presence of a posterior marginal 

 cellule. 



Length to tip of wings not quite 3 mill. One specimen, found dead in the 

 room where I keep my insects. 



| " Tarsi two-articulate, discoidal celluleopen, absent." (Psocus, Subgenus 

 D, Hagen.) 



Psocos abruptus, Hagen ! P. corruptus, Hagen. P. aurantiaccs, Hagen. 



Psocus geologus, n. sp. Yellowish brown, ranging to almost black. Eye3 

 normal; antennae normal, villose, fuscous. Feet pale, with the tarsi and tips 

 of tibiae sometimes fuscous. Wings hyaline, all with golden reflections; veins 

 black ; pterostigma triangular, rounded posteriorly, hyaline, with a small spot 

 at the basal angle ; posterior marginal cellule semicircular. 



Length to tip of wings H mill. Ten specimens, found in the drawers of 

 a geological collection, into which paper had been pasted. Very near salicis, 

 Fitch, but distinguishable at once by the pterostigma not being truncate. 



The normal neuration of psocus is, apparently, a discal bifurcation with the 

 anterior furcation throwing out one branch and the posterior one throwing out 

 two, in each case towards the margin. In the groups with the discoidal cellule 

 closed, the posterior furcation seems at first sight to throw out three branches 

 instead of two; but this is in reality caused by the submedian nervure, which 

 closes the discoidal cellule by uniting with the posterior furcation, afterwards 

 leaving that furcation and running to the margin. Any one may convince 

 himself of this fact by comparing those species where the submedian nervure 

 comes very close to the posterior furcation, but does not quite touch it, with 

 those where it does actually touch it. What I have here called the discal 

 bifurcation seems analogous to the "sectors" of the "arc" in the odonata ; 

 and the cross-vein from which it rises analogous with the " arc " itself. Dr. 

 Hagen has observed, that " the reticulation in P. abruptus and P. corruptus is 

 abnormal, and may constitute a distinct subgenus or rather genus." At first 

 sight there seems to be a tri- not a bi- furcation in these species, or in other 

 words, three sectors to the arc instead of two. But a closer inspection will show 

 that there are in reality only the normal number two the anterior one throw- 

 ing out its branch a short distance from the arc, and the posterior one throwing 

 out at tho usual distance one branch instead of two, which is the only abnormal 

 feature in the neuration of these two species. 



PERLINA. 



Pteronarcys nobilis, Hagen. Perla (Acroneuria) abnormis, Newm. 



[Sept. 



