No.2368. AMERICAN SUBTERRANEAN GALLS ON OAK— WELD. 20l 



having registered — 14° F. in the interval. On the 19th of the next 

 February over 200 were found alive in the cage, which had been 

 buried up in the snow for six weeks without a thaw. On March 12 

 there were two more out. In Florida pupae were found in galls on 

 October 11, 21, 23, and November 3, and the earliest record of finding 

 adults in the galls was November 20 and the earliest emergence 

 December 1. 



The life history suggested from the above data is that the galls 

 start in the autumn and get their full size quickly the first season 

 and that the larvae do not transform until the next autumn when 

 the galls are over a year old. After the larvae transform, the galls 

 soon turn brown, the proximal part about the larval cell becomes hard 

 and brittle, and during the winter the distal fleshy half of the gall 

 becomes converted into soft spongy granular tissue through which 

 the adults can easily chew their way (fig. 7) and it finally decays 

 away entirety leaving the hard wedge-shaped bases containing the 

 cells to persist for years. The adults either emerge in very late 

 autumn or very early spring, and are wonderfully resistant to cold. 

 But if there is an alternating generation it is unknown. 



Genus TRIGONASPIS Hartig. 



(Sexual generation.) 



In the Dalla Torre and Kieffer monograph of 1910 the sexual 

 generation of this genus is represented in the American fauna by 

 only one species, namely, radicis Ashmead. Two more are here 

 described and two are here transferred to Trigonasjris from other 

 genera. 



The galls of this group are all of the same type. They are all 

 white or rosj^, fleshy, fig-shaped, polythalamous, in hemispherical 

 clusters at base of tree or stump. They reach maturity quickly in 

 the spring, and with the escape of the winged flies either decay or 

 shrivel up into an unrecognizable hard but not woody dark mass. 

 They can not at present be distinguished except as host oak and 

 locality may be known. Galls of Belonocnema treatae Mayr are also 

 of this type but are said to occur in clusters on the small roots away 

 from the trunk of the tree. 



KEY TO SEXUAL GENERATION OF TRIGONASPIS 



1. Wings with at least 4 distinct dark spots. A red and black species from Califor- 

 nia obconica Weld, p. 202. 



Wings clear or at most faintly clouded, not spotted. Not red and black 2 



2 Wing with very faint clouds in apical cell. Female with interocular area at 

 least 1.4 times as broad as high. Hypopygium with spindle-shaped ventral 



spine radicola (Ashmead), p. 203. 



Wing clear. Female with interocular area not over 1.3 times as broad as high even 

 when measured in widest place. Ventral spine scarcely broadened 3 



