16 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [VolY. 



front wings ; smootli; joints 3, 4, and 5 cylindrical, and of equal thickness; 3 as long 

 as the other tv^'-o together ; 6 more slender at base, and with the apical unguis nearly 

 as long as 3. Thorax with mesonotal swellings small. Terminal distance between 

 1st and 2d discoidal veins of front wings nearly equal to that between this last and 

 the stigmal vein ; discoidals almost connected ; cubital obsolete at base ; subcostal 

 heavy ; stigma scarcely wider than subcostal si^ace, acuminate at tip, and with the 

 vein starting a little in front of its middle. Hind wings with the discoidals connected 

 at base, where the subcostal is slightly produced. Legs normal. Abdomen showing 

 about 30 pseudova, and with 4 dorsal rows of faint piliferous dots. Pupa with joints 

 1, 2, 4, and 5 of antennae subequal in length. The wingless forms are pale creamy- 

 yellow, with faintly dusky members. 



Missouri, Southern Texas, and Colorado (Eiley). May possibly be popularia, Fitch, 

 the description of which does not admit of identification. 



This gall occurs all over tlie West and Southwest, and while it nor- 

 mally occurs in the position and of the form described, it may occiu' on 

 any part of the petiole, and the opening may he more or less oblique, or 

 form a mere circular hole. Sometimes two and even three coalesce. 

 The lip-like bulging is, however, constant. In the galls, after they had 

 fallen to the ground, I have found in Southern Texas a number of large, 

 yellow, apterous females of an undescribed Phylloxera, surrounded with 

 their numerous eggs and with young of all sizes — a fact that would be 

 extremely confounding were Phylloxera and Pemphigus not so easily dis- 

 tinguished. 



PEMPHIGUS POPULI-EAMULOEUM, n. sp. 



[Forming an irregular globular gall {populi-ramuloriim), often somewhat flattened; 

 on the twigs of Populus ialsamifera in Colorado. The gall averages 15'^™ in diam- 

 eter, and opens in a suture sometimes transverse, sometimes oblique, but more often 

 longitudinal with the axis of the twig : exceptionally the opening is round aud bulging. 

 Green w^hen fresh, it becomes gray and woody with age. ] 



Pemphigus populi-ramulorum. — Winged female: Alar expanse 6.8'"'". Black and 

 pruinescent, scarcely distinguishable from populi-transversus, except by the more an- 

 nulate antennae, the 4th, 5th, and 6th joints of which are much narrowed at base. The 

 6th joint (including subjoint) scarcely as long as 3d. The pupa is yellowish, with 

 black eyes, and pulverulent. 



Colorado (Riley). 



Several of the species of Pemphigus forming galls upon Populus so closely 

 resemble each other that they could not weU be separated as species were 

 it not for the differences in the galls they i)roduce. Future careful in- 

 vestigation may show that the same species will produce different abnor- 

 mities, and be slightly modified in appearance according as it affects 

 different i>arts of the plant ; but until we have such proof, the presump- 

 tion is that the different galls are produced by distinct species, however 

 similar the architects are in general appearance. 



PEMPHIGUS ACEEIFOLII, n. sp. 



[Living in abundant and long cottony excretion, on the under side of the leaves of 

 Acer dasycarpum, causing them to curl, and exuding an abundance of thick and very 

 glutinous "honey-dew."] 



Pemphigus acerifolii, n. s^i. — Whujed female: Alar expanse IQi"™. Head and 

 thorax bluish-black. Abdomen black, covered with long cottony threads. AntennaB 

 reaching the wing-insertions; ambulations not conspicuous; joints 3, 4, 5, and 6 

 somewhat contracted at base and apex; apical unguis not perceptible; joints 5 and 6 



