412 MERISTIC VARIATION. [part t. 



'617. Prionus fissicornis: the female has 25, and the male 27 — 

 30, the note on the preceding species applying here. 



618. Polyarthron. A Prionid beetle, in which the male has curious 

 many-jointed feather-like antennae, according to Serville has always 

 47 joints, but Thomson (Syst. Ceramb., 1866, p. 284) says the number 

 varies with the species and individually. A male in Dr Sharp's col- 

 lection has 45 joints in each antenna and a female has 31 in each. 



619. Lysiphlebus is a Braconid (Hymenoptera) parasite on Aphides. 

 From a colony of Aphides on a bush of Baccharis viminalis 121 speci- 

 mens of Lysiphlebus were reared : of these 57 were males and 64 were 

 females. 



The number of joints in the antenna? varied as follows : 



Males. 



14 joints 18 specimens. 



15 37 



16 1 



15 on one side and 16 on the other 1 



Females. 



12 7 



13 54 



14 1 



12 on one side and 1 3 on the other 2 



In those having a different number of joints in the right and left 

 antenna?, the last joint of the antenna which contained the fewest 

 joints was longer than the last joint of the antenna with the larger 

 number of joints. Nevertheless this relation did not hold throughout ; 

 for example in the case of the male with 16 joints, the last joint was of 

 the same length proportionally as that of the males with only 14 joints. 

 As a rule the specimens with fewer antennary joints are smaller than 

 the others. 



Variations were also seen in coloration, in the proportional length 

 of the tarsi, and in the presence or absence of the transverse cubital 

 nervure, but none of the characters divided the sample consistently, it 

 was therefore inferred that the individuals belonged to one species of 

 Lysiphlebus, (L.citraphis, Ashm.) 



From another colony of Aphides living on a rose-bush 58 specimens 

 of Lysiphlebus were bred, and no chai'acters were found by which these 

 could be separated from those bred from the Aphis of Baccharis. In 

 the case of the second sample the joints of antenna? were as follows : 



Males. 



14 joints 10 specimens. 



15 19 



14 on one side and 1 5 on the other 2 



Females. 



12 2 



13 25 



