248 Annals Entomological Society of America [Vol. VI, 



two bristles stood out at right angles, or at least at a considerable 

 angle, to the longitudinal plane of the abdomen; whereas the 

 remaining bristles were barely elevated and extended over the 

 dorsum of the third segment. Thus these central bristles 

 stood out as two distinct macrochaetae. It not infrequently 

 happened however that these central bristles were not elevated 

 and hence they could not be readily distinguished from the 

 others of the marginal row and inference was naturally drawn 

 that they were not present. Their presence could usually 

 be detected by examining the sites of their insertions as com- 

 pared with those of the remaining bristles; the central pair 

 had their insertions very slightly anterior to the row of marginal 

 macrochaetae. 



The tegulae varied, as in L. sericata, from white to smoky; 

 in one lot of bred material particularly an excellent gradational 

 series, in respect to this character, was obtained. 



The apex of the first posterior cell of the wings was, unlike 

 the condition in L. sericata or L. caesar, longer than the anterior 

 cross vein. This character is best seen from the under surface 

 of the wing. It is apparently one of the best for separating 

 this species from L. sericata. There was often a short spur 

 at the angle of the fourth longitudinal vein. 



RESUME OF L. CAESAR. 



In all cases there were three strong ■ pairs of dorsocentral 

 bristles and there was no rudimentary or vestigial fourth pair. 



In all cases but one, two pairs of postacrostichal bristles 

 were found to be present. In this one exception there was 

 an extra pair erratically placed. 



The humeral bristles varied considerably. In the bred 

 specimens there were two flies with two pairs and one fly with 

 three pairs. The most common condition was two pairs, but 

 there were a number of specimens with an extra anterior bristle 

 on each side, and again others with a complete anterior fourth 

 pair. At the other extreme there was a fly with two bristles 

 on one side and three on the other. There was thus greater 

 inconstancy of humeral bristles in this species than in either of 

 the other two. It is interesting to note that it was always, 

 as in L. sericata and L. sylvarum, the anterior bristles and of these 

 the interior pair that were subject to variation. 



