116 PROC. ENT. SOC. WASH., VOL. 23, NO. 5, MAY, 1921 



material, it affords a good illustration of the folly of basing 

 genera upon such slight differences in the antenna. The mater- 

 ial under consideration, as already pointed out, has been exam- 

 ined by three different students of Chalcidoidea and accepted 

 by all three as a single species. Yet from an examination of 

 slide-mounted antennae alone, the four individuals, antennae 

 of which are figured, would probably be run in any of the 

 existing generic keys to three different genera. The genera to 

 which they would be assigned would depend largely upon 

 whether the individual making the examination chose to call the 

 eighth antennal joint a part of the club or a part of the funicle, 

 upon how many of the minute ring-joints he was able to see, 

 and upon whether or not the particular mount examined 

 revealed the suture dividing the ninth joint. The determina- 

 tion of the generic position would depend to a considerable 

 extent upon the individuality of the particular specimen from 

 which the antenna for mounting was taken but more largely 

 upon the accidents of mounting. 



The antenna of the male allotype of Pleurotropis utahensis 

 (Figure 1, E) is ten-jointed. The scape is only slightly more 

 dilated than in typical species of the genus. The flagellum 

 tapers from base to apex and the club is hardly differentiated 

 from the funicle although joints 9 and 10 are more or less anchy- 

 losed and probably represent the club. If so the funicle is 

 3-jointed as in typical Pleurotropis. There are three distinct 

 though minute ring-joints. 



Most writers have credited the genus Pleurotropis with only 

 one ring-joint. Waterston (Bull. Ent. Research, vol. 5, 1915, 

 p. 343) considers the ring a single joint but states that this joint 

 consists of two to three laminae which are distinctly separated 

 only ventrally. With this conception I can not wholly agree. 

 Mounts of antennae from many of the species in the National 

 collection have been examined with the result that in most cases 

 it has been possible to recognize three complete ring-joints. In 

 some cases there are apparently only two, while in a few in- 

 stances owing to the position in which the antenna was mounted 

 it was impossible to determine the number. The ring-joints are 

 always more or less telescoped into each other but are separated 

 both above and below. When the flagellum is bent upward it 

 tends to pull the ring-joints apart ventrally while pressing them 

 more closely together dorsally and this may account for the 

 impression gained by Waterston. 



It is the writer's belief that while Pleurotropis normally has 

 ten-jointed antennae in both sexes consisting of scape, pedicel, 

 three ring-joints, a 3-jointed funicle and a 2-jointed club, the 

 genus can not be limited to this antennal formula because one 

 finds all degrees of separation and solidification of the apical 

 two or three joints of the flagellum, it is not always possible to 



