1913] Variation in the Genus Lucilia. 243 



RESUME OF L. SERICATA. 



In all cases there were three strong pairs of dorsocentral 

 bristles, no rudimentary fourth pair. 



In 98.1% of cases there were three pairs of postacrostichal 

 bristles. One of the variations was an extra spasmodically 

 placed bristle of the mesonotum (postsutural). The other 

 variation was that of two postacrostichals only on the left 

 side; this may indicate a past connection between the forms 

 with typically three pairs and those with typically two pairs 

 (L. caesar). 



As regards humeral bristles 88.7% of the flies examined 

 were supplied with four strong ones on each side. The varia- 

 tions ranged between a form with two on one side and three on 

 the other and the typic form with four on each side. The 

 anterior bristle was always the one to be lost. 



The interior bristle seems to have a taxonomic affinity 

 toward the anterior bristle, as in the case of the latter aborting 

 it was usually found that the interior bristle was weak (in one 

 case it was lost completely on one side). 



There were in 96.9% of cases 3 sternopleural bristles on 

 each side. This is a generic character and yet there was 

 variation, not in the species as a whole, but in individuals. 

 These variations were in an increase and decrease of these 

 bristles in both number and strength. In all cases the posterior 

 bristles were constant and the anterior alone became modified. 



The ocellar bristles varied according to sex. 



82.5% of the female flies had two well-defined pairs. In 

 the great majority of these cases the anterior pair was longer 

 and stronger than the posterior pair, but at the same time the 

 latter pair was sufficiently strong to warrant the application of 

 the term 'bristles'. As to position the anterior pair had their 

 insertion within the ocellar triangle and the posterior pair 

 had theirs outside of the triangle and immediately posterior to 

 it. As to the exceptions to this normal condition of two pairs 

 there were a few cases in which the post, pair were weak; one 

 case in which the two pairs were both exceptionally strong; 

 several instances in which there was an extra bristle developed 

 on one side within the ocellar triangle and posterior to the 

 normal anterior pair; and finally a few instances in which 

 there was an extra pair of bristles developed within the ocellar 

 triangle and post, to the ant. pair. 



