14 Thomas Albert Williams 



nent than in the apterous female ; head and thorax covered with 

 whitish powder. The antennae are 6-jointed by the division of 

 the third (?) larval joint into three, the second joint shortening; 

 III to VI are marked with transverse irregular interruptions lined 

 with a thin membrane, while the terminal and subterminal joints 

 contain sensitive glands, as do also these joints in the larva and 

 apterous female. Length 4 to 5 mm. Expanse 10 to 12 mm.'" 

 All the forms of Pern, fraxinifolii Riley were found on the 

 same trees and at the same time but these differ very materially 

 from the above, 

 n. Pemphigus vagabundus (Walsh). 



Walsh, Proc. Ent. Soc. Phil., I, p. 306 (1862). Byrsocrypta vagabunda. 



Packard, Guide to Study of Ins., p. 524, 2d Ed. (1870). Pemphigus 

 vagabundus. 



Thomas, Ins. 111., 8th Rep., p. 151 (1879). 



Oestlund, Syn. Aph. Minn., p. 22 (1887). 

 Stem-mother: Very large, subglobose, pale yellowish green. Head 

 brownish. Antennae 4-jointed; III very long, IV with an unguis nearly 

 as long as the remainder of the joint; I, II and III pale, IV dusky. Eyes 

 imperfect but quite distinct and black. Beak reaching to middle coxae, 

 black tipped. Legs short, pale, with brownish joints and tarsi. Coxae 

 brown. Length of body 5.10 mm., width 4.25 mm. 



Pupa greenish yellow. Antennae 6-jointed; VI with unguis longer than 

 III. Legs, wing-pads and antennae pale, tips of antennae and tarsi dusky. 

 Winged viviparous female: Head and thorax shining black. Eyes dark 

 red. Antennae reaching to rear of thorax, black, with paler articulations; 

 III with 8-10 transverse sensoria, as long as IV, V and VI without the 

 unguis and about as long as VI with its unguis; IV, V and lower 

 part of VI subequal; unguis of VI twice as long as the lower part; III 

 cylindrical; IV, V and lower part of VI club-shaped. Wings delicate; 

 subcostal and stigma conspicuous, yellowish brown, the latter rather short; 

 oblique veins very slender, hardly perceptible. Abdomen greenish, show- 

 ing the embryos very plainly. Legs blackish. Beneath the fore part, of 

 the body is dusky, the mesosternum black and the abdomen pale yellowish 

 green. Length of body 2.70 mm., to tip of wings 4 mm. ; alar expanse 

 7.50 mm. 



Forming a large irregular gall at the ends of twigs of cotton- 

 wood (Populus monilifera) and balsam poplar (Populus bal- 

 samifera). Weeping Water, Lincoln, Squaw Canyon, Ashland. 

 The past season galls were found June 13 containing stem-mother 



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