310 



tions botli of American and foreign aphid s at ray command, I have 

 arrived at the couclusiou that the species infesting so disastrously the 

 various kiuds of cacurbitaceous plants is identically the same as A})his 

 (/ossi/pii Glover, and that the descriptions of Aphis citrifolii Ashm. in 

 part; A. citrulli Ashm.-, A. cucumerifi Fovhes, ami prohnhly A. forbesi 

 AYeed, are referable to the same species. I am also of the opinion that 

 pai't of the description of A. rumicis, by Prof. C. Thomas, may be 

 referred to it. 



Whether or not any of the described European species are identical 

 with it, I am at present unable to decide, since none of the descriptions 

 fit our American insect exactly. 



From the very large quantity of material at my command, I have 

 been enabled to observe extreme variability of coloration both in adults 

 and larva^, Avhether on the same or different plants, whereas all the 

 important structural characters remain the same m all. 



The darkest of its apterous forms, and also the pupse, bear a great 

 general resemblance to A. rumicis, which, however, is a considerably 

 larger and more robust insect, having longer and stouter antenucTe and 

 larger nectaries, while the antenna! sensoria are more numerous and 

 more irregularly jirranged than in this species. 



The first account of this plant-louse was published by Prof. Townend 

 Glover in the Patent Office Report for 1854, p. 62, with figures on 

 Plate 3, which article was reproduced in the Patent Office Report for 

 1855, p. 68, Plate vi, Fig. 2, though the specific name was first applied 

 in the Report of the Department of Agriculture for 1876, p. 36, Fig. 39. 



Professor Glover's account of this plant-louse is in substance as 

 follows: 



When the cotton jilant is very youug and tender, it is particularly subject to the 

 attacks of the cotton louse, and the constant puncturing and drainage of sap from 

 the young leaves enfeeble the plants to such a degree that the leaves are caused to 

 curl, turn yellow, and subsequently withfer away and fall to the ground ; and although 

 young i^lants are most subject to these attacks, he has seen old stands of cotton in 

 Georgia with their young shoots completely covered with this pest as late as 

 November. 



In 1880 Mr. Wm. H. Ashmead redescribed this species in his pam- 

 phlet on " Orange Insects," under the name of Siphonophora citnfolii, 

 which he found to be infesting his orange trees, without being aware 

 that the same insect infests also cotton and had been described pre- 

 viously. 



Again in 1882, Mr. Ashmead, in a iiaper on the "Aphididae of Flor- 

 ida" in the Canadian Entomologist (vol. xiv, p. 91), in discussing 

 dimorphism among insects, besides reproducing his original descrip- 

 tion, makes the serious mistake of describing on page 92 another species 

 as a dimorphic form of his citrifolii, which, however, according to the 

 characters given in this description, is neither a true Aphis nor a 

 Siphonophora, but appears to belong to the genus Rhopalosiphum. 

 Mixed colonies of closely related and other species of aphides are fre- 



