1913] Variation in the Genus Lucilia. 245 



at the base. Thus for this species at least the color of the palpi 

 is not constant and the infuscation at the tip has no specific 

 value. 



In the color of the first segment of the abdomen was found 

 an excellent secondary sexual character. In all cases it is the 

 dorsal area of the segment that is referred to and not the 

 ventral. 



In all males examined the first segment was, at least super- 

 iorly, black. In the females this segment varied from the 

 color of the remaining segments (i. e. abdomen unicolorus) to 

 a shade darker; there were few examples of this latter condition. 



On the second abdominal segment there was superiorly 

 a row in both males and females, of fairly strong marginal 

 macrochaetae. These marochaetae were stronger .centrally, 

 then became weak and finally became strong again at the 

 sides. These bristles varied slightly, but not to any marked 

 degree; in a few cases they were strong and in a few cases weak; 

 in two instances (1 cf and 1 9 ) the two median bristles stood 

 out more prominently thus approaching the condition in L. 

 sylvariun. 



The tegulae varied from white to brown. This variation 

 was evident in all the series of flies of all species and in one lot 

 of L. sylvariim bred from a single egg cluster all intermediate 

 stages were found between the pure white and the brown 

 conditions. 



Before passing to the next character it may be well to 

 observe that all flies killed and pinned soon after the time of 

 issuance have pure, or almost pure, white tegulas; and that 

 only in flies that have either been collected, or bred through 

 and left in a cage for ten days or more, have the brown-tinged 

 tegulae been observed. This seems to indicate that the tegulae 

 darken as the fly grows older. 



It was found that the width of the apex of the posterior 

 cell in comparison with the length of the anterior cross-vein 

 was slighth^ or distinctly shorter; the only exception to this 

 was in the case of two flies in which the lengths were equal. 

 This character has not previously been made use of. It is 

 apparently very constant and serves as a sepa;-ating character 

 for this species from L. sylvarum. 



The character is best seen when the wing is viewed from 

 below. In vein 4 there was in no case any appendage — even 

 rudimentary — at the angle. 



