THE CANADIAN ENTOMOLOGIST. 93 



ON THE GENERA VENUSIA, EUCHCECA AND HYDRELIA. 



BY LOUIS B. PROUT, LONDON, ENGLAND. 



In Mr. PearsalPs valuable " Review of our Geometric! Classification 

 — No. 3,"* a venational character is not mentioned, which — with the 

 rarest possible exceptions, none being known to me save Alsophila — is as 

 reliable as the structure of veins 5 and 8 of the hind wings, and which has 

 been used as generic in the Larentiinse ( = Hydriomeninae) by Hampson, 

 and more recently by Dr. Turner in an able revision of the Australian 

 genera of the subfamily. f I allude to the structure of the discocellulars 

 of the hind wings. Ignoring minor variations which Mr. Pearsall might 

 prefer to place in his " auxiliary group," there are two essentially different 

 forms : (1) simple, or with a single angle inwards, marking the point of 

 contact of the middle discocellular with the lower, vein 5 being in these 

 cases either from the angle or from above it (or from the middle or above 

 it where there is no appreciable angle) ; (2) biangulate, with vein 5 from 

 the lower angle, thus from nearer (sometimes very much nearer) to 4 than 

 to 6. The first form may be seen in Eudule, Eupithecia, Xanthorhoe (so 

 far as it is homogeneous), and others, as well as in the vast majority of 

 non-Larentiids ; the second form in Rachela, Oporinia ( = Epirrita), 

 Hydriomena (except a few dissonant species which Hulst has included), 

 Marmopteryx, and many others. 



That this distinction is correlated with real phylogenetic differences, I 

 have little doubt. Several " genera " of Guenee, upon whose system I 

 worked in my early days, and which dissatisfied me profoundly on larval 

 grounds, have proved to divide very satisfactorily with the aid of the 

 discocellular character — for example his Melanippe and Anticlea. 



Now, it happens that Euchceca (type obliterata, Hufn.) and Hydrelia 

 (type testaceata, Don.) fall into group 1 (with discocellulars simple), and 

 Vennsia (type cambrica, Curt.) into group 2. There was much discussion 

 on the American representatives of these a few years ago, and much useful 

 revision was done, notwithstanding some regrettable differences of opinion. 

 But no one seems to have noticed that cambrica, Curt.; comptaria, Walk.; 

 Pearsalli, Dyar, and duodecimlineata, Pack. ( = unipecta, Pearsall), which 

 are so much alike superficially, all agree in the hind wing venation 

 (discocellulars biangulate). while lucata, Guen., and the much-enduring 



*Can. Ent., Vol. 39, page 91. 



tProc. Roy. Soc. Victoria, Vol. 16 (New Series), page 218. 



