176 Journal of Agricultural Research Voi. xvm, no. 3 



plant in natuie. The natural food plants of P. ainsliei are Polygonum, 

 ragweed, and similar plants; and it is frequently found in corn associated 

 with P. nuhilalis, for which its larva is easily mistaken. 



In fact it is impossible to separate the two on superficial characters, 

 and in structure they so closely resemble each other that a careful micro- 

 scopic examination is necessary to determine which is which. There is 

 a slight difference in the size of the heads of the mature larvae. That of 

 P. nubilalis is slightly larger, as shown by the drawings (PI. 10, A, G) ; but 

 this character is comparative and impracticable for purposes of distinc- 

 tion, since it is necessary to have specimens of both species of the same 

 stage of development for comparison and to be certain at the same time 

 of their instars, something that is rarely possible. The shape of the anal 

 plate used by Miss Mosher is unreliable, both species exhibiting the same 

 forms and the same amount of variation. The clear spots indicating 

 certain muscle attachments on the abdomen are scarcely more reliable. 

 The character is extremely elusive and subject to enough modification 

 to leave one in doubt except with most typical specimens. There seems 

 to be only one reliable character — namely, the arrangement of the setae 

 and puncture of the anterior epicranial group. In P. nubilalis, as men- 

 tioned, A^ is approximate to A^ and A^, A\ and the puncture A* are in 

 a straight line or with the puncture postero-ventrad of A^. In P. 

 ainsliei A^ is as near to A^ as to A^ (or nearer), the three setae forming 

 almost a right angle with the puncture A* lying postero-dorsad of A^, 

 the setae *A^ and A^ and the puncture forming an obtuse angle. There 

 is some variation in the degree of distance separating A^ and A^ in indi- 

 vidual specimens and some asymmetry, especially in P. nubilalis; but 

 the character seems to hold, and it has been found sufficiently constant 

 through large series to enable accurate determination of all larvae so far 

 submitted for identification. The pupa is easily distinguished by the 

 front, which is developed into a knob-like projection (PI. 9, A). Other- 

 wise it is much like that of P. nubilalis, though as a rule smaller and a 

 trifle more slender. The average length is 12 to 14 mm. 



PYRAUSTA PENITALIS 



Pyrausta penitalis Grote, 1876, in Canad. Ent., v. 8, p. 98; Dyar, List No. Amer_ 

 Lepidop.,p.39i,no. 4439. 1902 

 Pyrausta nelumhialis Smith, 1890, in Ent. Amer., v. 6, p. 89; Dyar, List No. Amer. 

 Lepidop., p. 391, no. 4439. 1902 



ADULT 



The adult of this species, especially the female, resembles P. nubilalis more closely 

 in superficial characters than does P. ainsliei. In fresh specimens the darker shadings 

 have a more distinctly ferruginous tint. As in P. nuhilalis, there is considerable 

 variation among both males and females, and the males have tlie same sex scaling at 

 the base of the inner margin of the forewing; but the darkest male of P. penitalis is 

 never quite so dark as a pale tmrubbed specimen of P. nubilalis. The hindwing is 



