THE CANADIAN ENTOMOLOGIST. , 91 



and able investigations and experiments with the diurnal Lepidoptera have 

 thrown such a tiood of light on dimorphism and what really constitutes 

 " a species ;" and last, but not least, Prof. C. V. Riley's similar discoveries 

 among the Phylloxerte and Pemphiginse. All have done much towards 

 elucidating the vexed question. 



Among the Aphididse proper, although it has often been suspected in 

 America, no recorded instance of dimorphism among them, that I am 

 aware, exists. The discovery of its occurrence in the Orange Aphis, 

 Siphonophora citrifolii, described by me in my pamphlet on " Orange 

 Insects," in the fall of 1880, therefore is of great interest, and no doubt will 

 prove such to many readers of the Can. Entom. 



From observations made this year I find that from an egg laid by a 

 fall oviparous female hatch the brown-black and black winged male and 

 winged viviparous female, which 1 describe as follows : 



Young. —Length .02 inch. Dark greenish brown, with dark eyes and 

 glassy white antennae and legs. 



^, — Length .04 inch. Color brown and brown-black; antenna 

 brown, legs pale or yellowish, posterior femora slightly shaded above with 

 brown or black ; feet reddish ; nectaries shorter than in female ; wings 

 hyaline, stigmal spot pale. 



These are rare among the first broods, and afterwards almost or entirely 

 disappear. 



^ Apterous. — Length .05 to .06 inch. Broadly ovate. Dark brown- 

 ish black. Head between antennae reddish ; antennae 7-jointed, pale 

 yellowish, apical ends of joints 3, 4 and 5 brown, 6th shortest, 7th long, 

 setaceous ; legs pale yellow, latter two-thirds of femora brownish or 

 blackish, tips of tibiae and claws brown ; nectaries slightly thickest at 

 base, black and cylindrical ; cauda distinct. 



%. Winged viviparous. Length .06 inch. Color black and shining; 

 eyes red-brown, tubercles of antennae black, vertex of head reddish ; 

 rostrum reaching back of middle coxce ; antennae not quite reaching to 

 tip of abdomen ; abdomen variable, brown-black, brown or olive-green ; 

 nectaries long, cylindrical and black; cauda long and recurved, dark; 

 wings hyaline, stigma rather broad, brown, obliquely sharpening to a point 

 at outer edge towards apex ; stigmal vein strongly curved, three oblique 

 veins, the third forked ; hind wings with two oblique veins, in some speci- 

 mens but one. 



