"90 Fiftieth Report ox the State Museum 



Pemphigus rhois (Fitch). 



The Sumac-Gall ApJiis. 



(Ord. Hemiptera : Subord. Homoptera : Fam. Aphidid.^:.) 



Fitch: in Month. Journ. N. Y. St. Agricul. Soc. for Aug., 1866, p. 73 



(described, as Byrsocrypta rhois with remarks). 

 Walsh : in Proc. Entomolog. Soc. Phil., vi, 1866, p. 281 (referred to 



Mclaphis). 

 Packard: Guide Study Ins., 1869, p. 524, fig. 523 (brief mention). 

 Walsh-Riley : in Amer. Entomoi., i, 1869, p. 108, fig. 89 (brief mention, 



in Illinois and New York). 

 Thomas: 8th Rept. Ins. 111., 1S79, pp. 152-153, fig. 28 (brief mention). 

 Lintner : 3rd Rept. Ins. N. Y., 1887, p. 142 (from Schenectady); in 



Country Gent., lix, 1894, p. 686 (brief account); loth Rept. 



Ins. N. Y., 1895, p. 503 (abstract of preceding, all as Melaphis). 

 Oestlund : Bull. 4 Geolog. and Nat. Hist. Surv, Minn., 1887, p. 23 



(bibliography, description, remarks). 

 Smith : Cat. Ins. N. J., 1890, p. 451 (listed). 

 Riley-Howard: in Insect Life, v, 1892, p. 145 (tannin in gall). 



This insect is rarely seen, except by those curious enough to cut open 

 one of the galls that it forms on the leaves of sumac. If the examination 

 be made in September, it will be found lightly packed with particles of 

 white flocculent matter which are the cast skins (exuviae) of the lice at 

 their successive moltings, hundreds of yellow-green wingless aphides, 

 with wing-pads upon their sides (the pupal stage of the insect), and a 

 smaller number of matured winged forms. A little later all will have be- 

 come winged. 



This insect was referred to the genus Byrsocrypta by its describer. Dr. 

 Filch, in 1866. Shortly thereafter Mr. Walsh made it the type for the 

 new genus Melaphis, but upon insufificient grounds, according to Mr. 

 Oestlund, who has recently placed it in the genus Pemphigus. 



Description of the Gall and Immature Aphides 

 The galls have been described by Dr. Fitch as follows : 

 Resembling little round balls of difterent sizes, the largest measuring 

 an inch in diameter, their surface uneven and slightly knobby in places, 

 and covered with fine erect white hairs ; their color pale buft'-yellow or 

 greenish-yellow, and on the side exposed to the sun bright crimson-red. 

 Attached to the leaf by a narrow neck, opposite which, on the upper side 

 ■of the leaf, is a thickened wart-like elevation, or sometimes higher con- 

 ical protuberance, which is also covered with erect white hairs ; and the 

 leaf itself is partly withered, and turned red or yellow. Cavity inside 

 large; in the smaller galls filled with small, oval, pale dull yellow lice of 

 different sizes, their eyes black, their feet and antennae white, the larger 

 ones measuring 0.03 in length, and some of these larger ones thinly 



