54 



The Irish Naturalist. 



Each of the eleven segments of the mature larva is 

 readily divisible into eight distinct areas (Fig. i.) : — a dorsal 

 area (d), a ventral area (v), and on each side a latero-dorsal 

 (l.d.) a lateral (/.) and a latero-ventral area (Lv.). Spines 

 are not borne on all these areas. In Hypcderma hcvis 

 the ninth, tenth and eleventh dorsal areas are devoid of 

 spines, as also are the tenth and eleventh ventral and 

 the ninth, tenth and eleventh latero-ventral areas ; ^hile 

 the latero-dorsal and lateral areas bear no spines after 

 the fifth segment. 



m CP = 



Fig. 2, Variation in the spiny armature of the right eighth latero- 

 ventral area in ten specimens (a-k) of the fourth-stage larva of H. bovis. 



X 20. 



The variations occur not only on corresponding areas 

 in different specimens but also on corresponding areas on 

 the right and left sides of the same specimen. The diversity 

 may be observed on any area that is selected for comparison. 

 It is well marked, for example, on the " bosses " of the 

 latero-ventral areas. Here the spines, pointing away from 

 the head, are frequently of a very irregular shape. They 

 are in some cases quite conspicuous, but in others are 



II mm. 

 I ^ 



