3l6 KELLOGG AND BELL 



On the right side : 13 individuals have 3 hairs, 49 individuals 

 have 4 hairs, 2 individuals have 5 hairs. 



On the left side : 14 individuals have 3 hairs, 48 individuals 

 have 4 hairs, 2 individuals have 5 hairs. 



The mean on right side is 3.83, on left side 3.81 ; the standard 

 deviation on right side .453, on left side .463 ; the coefficient 

 of variation on right side is 11.98, on left side 12.16. 



From these figures it is seen that in this species of Li;peii7'iis 

 the variates possessing three hairs greatly outnumber the vari- 

 ates possessing five hairs. This might be interpreted to mean 

 that the species is tending toward a form possessing three tac- 

 tile hairs instead of four, or alternately that the present form 

 with four hairs is developing (evolving) from an older form with 

 three. The coefficients of variation for this character are much 

 larger (twice as large) in this species than in L. ccler. 



Examining the distribution of the variations by isolated 

 groups of individuals (each group from a single bird host) the 

 thirtv-one variations are distributed among eleven groups out of 

 the total twenty-nine groups. In no group in which there was 

 a case of the occurrence of 5 hairs, was there an occurrence of 

 3 hairs (the largest group in which 5 hairs occurred contains 

 only five individuals). In a group of twelve individuals three 

 have 3 hairs on each side, and a fourth has 3 hairs on one side 

 and 4 on the other, while the remaining eight have 4 hairs on 

 each side ; in a group of ten individuals three have 3 hairs on 

 each side, a fourth has 3 hairs on one side and 4 on the other, 

 while the others have 4 hairs on each side. 



With regard to correlation between right and left side, forty 

 four individuals of sixty two (in which the hairs on both sides 

 could be accurately determined) have 4 hairs on each side ; 

 twelve have 3 on each side, two have 4 on one side and 5 on 

 the other, and one has 5 on each side. 



Variation in the Character of the Elytral Striae of Pterosti- 

 chus sp. (Predaceous Ground Beetle). — The ground beetles of 

 the genus PtcrostlcJuis have about ten fine longitudinal grooves 

 on each elytron (Fig. 81). These grooves present manifold 

 variation in their make-up, an}^ one appearing as a continuous 

 line, as a broken line, as a forking or branching line, or coa- 



