GALL APHIDS OF THE ELM. 221 



O.I2 mm.-0.14 mm.; VI, 0.13 mm.-o.i6 mm.; Ill exceeding 

 IV+V and less than V+VI. Annulations III, 18-22; IV, 4-7; 

 V, 7-10; VI, 9-1 1. The antenna of the pupa previous to the 

 molt shows, through the smooth pupal segments, the annulations 

 of the mature insect like a coiled wire (fig. 149). 



The wings (fig. 146) are normally as usual for Pemphigus, 

 but M in this species is not very stable, a branch of this vein 

 being not uncommon which gives us the wing of a Schisoneura. 

 Fig. 147 gives a weak example of this where M is branched 

 merely at the tip. This tendency was commented upon by 

 Walsh in his first record of the insect. Professor Oestlund 

 states that it is a very common tendency in Minnesota, and 

 the slide from him which is labeled "i25/'98 (383) B-64. 

 7/12" has 3 winged specimens, one of which has M branched 

 ill both wings and the other two have M simple on one side 

 and branched on the other. Of 18 specimens collected by Mr. 

 Davis, 7 July, '07. Leroy, Illinois, 4 specimens had M branched 

 on one side and one other had one M and one Cu branched. 



The gall which was used for Fig. 150 is over i^ in. (35 mm.) 

 long. Besides this I have seen only 4 or 5 galls of this species 

 from Minneosta and Illinois, none of which were so large. Mr. 

 J. J. Davis measured one gall of P. ulmifiisus collected at Villa 

 Ridge, in Southern Illinois, June 4, 1892, and found it to be 

 22 mm. long, 6]^ mm. wide at widest point and 2}{\ mm. wide 

 at the neck. 



Mr. Sanborn quotes the following description of the gall, 

 which is the best available, for which reason I am glad to make 

 use of it in this connection: 



"This gall occurs on the dorsal side of the leaf of the elm (i'hiius 

 aincricana?). The gall is large and elongated, tapering at both ends; 

 sides sunken and irregular, due to the thin wall of the central cavity; 

 2y2 c. in height and i c. in. at its greatest diameter. The walls are of 

 a leathery texture, green when young, turning to a straw color upon 

 reaching maturity. The gall is firmly fastened to the leaf. The internal 

 side of the gall is covered with plant-lice which emerge through a crack 

 which occurs along the side of the gall, or some few through the small 

 opening on the ventral side of the leaf." 



The original "description" occurs in an incidental manner in 

 a foot note and as it is no longer easily accessilile it is quoted 

 entire as follows : 



"The Red Elm, or Slippery Ehr, as we have ascertained by c'os? and 

 long-continued observation, never bears these cockscomb-like galls. But 



