222 MAINE AGRICULTURAL EXPERIMENT STATION. I91O. 



there is occasionally found upon the upper face of its leaves in small 

 numbers, a solitary gall with quite a thin rind, about an inch long, shaped 

 much like one of those depicted in figure 86,* and hitherto undescribed. 

 It is made by a species of plant louse belonging to the same genus 

 (Pemphigus) as Fig. 88.t In Europe a well known elm-gall (ulmi) 

 is made by another genus of Plant-lice {Byrsocrypta, Haliday = Tet- 

 raneura, Hartig). So that on the same genus of trees, the Elm, we have 

 three distinct galls made by three distinct genera of plant-lice; the more 

 general rule being that the same genus of gall-makers attacks the same 

 genus of plants. The above described gall on the Red Elm which we 

 may call the Spindle-shaped Elm-gall (Uhni fustts), was first brought to 

 our notice by Dr. W. M. Smith of New York; but we have since found 

 several specimens in South Illinois. The winged insect (Pemphigus 

 ulmi-fusus, n. sp.) which only measures 0.07 inch to the tips of the 

 wings, and is of a uniform dusky color, occurred July nth. Out of 

 28 specimens, two have both wings, and one a single wing veined pre- 

 cisely like those of Eriosoma (Fig. 70, c. p. 82) — thus affording a prac- 

 tical exemplification of how one genus of plant-lice may gradually in 

 the course of indefinite ages merge into another." 



Bibliography. 

 1869. Pemphigus iihnifusus Walsh: — Am. Ent. Vol. i, page log, foot 



note. Original description. 

 1879. Pemphigus ulmifusus, Thomas : — Rept. Ent. 111. VIII, (Thomas 



III) page 153. Brief remarks. 

 1887. Pemphigus ulmifusus, Oestlund : — Aph. of Minn., page 24. Listed 



for United States. 

 1890. Pemphigus ulmifusus, Packard : — Forest Insects, page 283. List 



of insects injurious to elm. 



1901. Pemphigus ulmifusus. Hunter : — Aph. of N. A., page 79. B"b- 



liography. 



1902. Pemphigus ulmifusus, Cook : — Galls and Insects Producing Them. 



Ohio Nat. Vol. II, No. 7, p. 265 and Fig. 14, a. b. Discussion 

 of structure of gall. 



1903. Pemphigus ulmifusus. Cook : — Galls and Insects Producing Them. 



Ohio Nat. Vol. Ill, No. 7, p. 425 and Fig. 49, a. b. Discus- 

 sion of structure of gall. 



1904. Schizoneura n. sp. : — Sanborn. Kansas Aphididae. pp. 28, 29 and 



Plate VI, fig. 41, 41a. First real description of this species. 

 Also a description of the gall by Mr. Burrows. This species 

 described and figured as Schizoneura from a specimen having 

 M forked as is not unfrequent with this species. 



1905. Pemphigus ulmifusus. Cook : — The Insect Galls of Indiana. 



(From 29th Ann. Rept. of the Dept. of Geol. and Nat. Re- 

 sources of Indiana. 1904, pp. 801-867) p. 849. Bibliography 

 in part. 



*A reference to the grape-vine filbert gall, Vitis coryloides. 

 f i. e. Pemphigus vagabundus. 



