242 [September 



Jlucns Harris all the oak-apples tilled with a spongy substance, which I 

 found in the environs of Washington. 



Already then, however, I noticed two varieties of this gall, the one with 

 a glossy, the other with an opaque surface (Compare 1. c. p. 56). 



These two varieties proved since to occur on two different kinds of oaks 

 and therefore, very probably, to constitute two species, although the gall- 

 flies, obtained from them, hardly show any difference. The gall-fly from 

 the oak-apple No. 3 (1. c. p. 58), which I did not know at the time, but 

 for which I proposed by anticipation the name of C. q^. inanis, has also 

 been reared by me since, and likewise closely resembles the other two gall- 

 flies. Thus we have three (or perhaps four, as will be seen below) differ- 

 ent and easily distinguished oak-apple galls, occui-ing on diflFerent species 

 of the red-oak group, but all three producing uncommonly similar gall-flies. 



The fourth oak-apple gall, peculiar to the same group of oaks, that of 

 O. q. aciculafa, discovered by Mr. Walsh, gives a totally different fly, as 

 the 9 bas 14- and not 13-jointed antennae. 



I distingui.sh therefore, at present, the following oak-apple galls and 

 their gall-flies : — 



Q. COCCINEA. Scarlet Oak? Larye^ more or less round gall, not at- 

 tenuated towards the basis; surface glossy ; shell thin and hrittle; on the 

 inside whitish filaments radiating from the kernel to the shell. Diameter 

 about an inch. C. Q. inanis (3. S. (Synon. 1. c. No. 8, p. 58, and pro- 

 bably C. confiuens Fitch, non Harris.) 



Two 9 specimens obtained from the galls on the 20th of June, 1862, 



answer to the following description : — 



Head black, deeply, irregularly sculptured on the front and vertex; face finely 

 pubescent, rugose ; antennte 1.3-jointed, brown or reddish-brown, especially to- 

 wards the tip. Thorax black, deeply, irregularly rugose, finely and sparsely pu- 

 bescent; three deeper longitudinal furrows, converging towards the scutellum, 

 may be distinguished among this rugosity; their bottom is intersected by numer- 

 ous transverse ridges and wrinkles. These furrows are deepest and broadest near 

 the scutellum: the intermediate one is gradually attenuated towards the collareJ 

 the anterior end of the lateral ones, which runs towards the shoulders, can be seen 

 onh' when the insect is kept in a certain position towards the light. Near the an- 

 terior end of the intermediate furrow and parallel to it, there are smaller, rather 

 indistinct, longitudinal furrows and ridges. The pit at the basis of the scutellum 

 is large, divided in two by a longitudinal ridge; its Ijottom, although glossy, is 

 marked with transverse ridges. Abdomen brownish-red, glossy ; the large basal, 

 in reality the second, segment (see 1. c. p. 48, foot-note) is perfectly smooth, the 

 other segments show a minute punctation : (the posterior edge of the smooth seg- 

 ment shows traces of a similar iJUiictution. but they are so minute, as to be hardly 



