THE CANADIAN ENTOMOLOGIST. 285 



In a recent letter from Professor C. P. Gillette, he writes that he has 

 examined a few species, contained in the collection of the State Agricul- 

 tural College of Colorado, namely : Brachycolus Ballii^ Gill.; Callipterus 

 sp., C. discolor, Mon,; Drepaiiosiphum Braggii^ Qr\\.) D. aceri/olii, Thos., 

 and Chaitophorus fiigr(e, Oest., and all bore sensoria on the hind tibiae of 

 the sexual females, they being rather obscure in the species of Callipterus 

 and Brachycolus. 



I have found these tibial sensoria on the oviparous females of Sipha 

 flava, Forbes ; Callipterus trifolii^ Mon.; Aphis brevis, Sand.; A. tiiaidi- 

 radicis, Forbes; A. Folsomii, Davis; Myzus elceagjii (?), Del Guer.; 

 Macrosiphum liriodendri, Mon.; Rhopalosiphum berberidis, Kalt., and 

 Drepa?iosiphum aceri/olii, Thos. 



Thus we find that these sexual tibial sensoria have been found present 

 on species representing twelve different genera, namely : Macrosiphum, 

 Myzus, Rhopalosiphum, Drepanosiphum, Aphis, Sipha, Siphocoryne, 

 Chaitophorus, Callipterus, Toxoptera, Brachycolus, and Hormaphis. 



I have examined many species for these tibial sensoria, and have 

 never found them present on the hind tibise of viviparous females or 

 males, but have always found them present on oviparous females. 

 Although a positive statement can not now be made with our present 

 knowledge, still it is quite probable that the hind tibise of the oviparous 

 females of the Aphididce, or at least of the subfamilies Femphigi/ice, 

 Schizo?ieurince, Lachnijtce, and Aphidince, are usually noticeably swollen, 

 and always bear more or less distinct and numerous sensoria. I know of 

 no other definite character for the distinguishing of the viviparous and 

 oviparous females, excepting the presence of either embryos or eggs in the 

 body. Mention has been made by several authors that the oviparous 

 females of certain species hold their bodies vertical to the surface upon 

 which they are resting. I have observed this characteristic position as 

 common to the sexual females, especially with Sipha flava and Aphis 

 maidi-radicis, but I find that it is not constant with all species, nor is it 

 always the case with the two species above mentioned. 



Explanation of Plate 8. 

 Hind tibiae of oviparous females of (i) Macrosiphum liriodendri, 

 Mon.; (2) Aphis Folsomii, Davis; (3) Drepanosiphum aceri/olii, Thos.; 

 (4) Rhopalosiphum berberidis, Kalt.; (5) Aphis maidi-radicis, Forbes; 

 (6) Myzus elceagni (?), Del Guer.; (7) Sipha /lava, Forbes ; and (8) 

 Callipterus tri/olii, Mon. 



