r922. Phibbs. — The Larval Mouth-Hooks of Hypoderma. 27 



anterior end and the blunt rear end of the mouth-hook of 

 H. bovis are so distinctly different from the sharply pointed 

 anterior end with a well-formed tooth some distance below 

 and the slightly pointed rear end of the hook of H. lineatum 

 that the two species can be separated almost at sight in the 

 first instar." Laake's observations of the second instar 

 were made on specimens of H. lineatum only. From an 

 examination of several specimens of H. bovis, taken from 

 the gullets of Irish cattle, it is clear that this distinction is 

 equally evident in the second stage. 



Speaking of the mouth parts of the first stage larva 

 Carpenter and Hewitt (2) say — " We find that in H. bovis 

 the mouth-hooks articulate directly with the phar3mgeal 

 sclerites, the paired' hypostomal sclerites that intervene in 

 most half-grown or full-grown muscoid larvae not being 

 present ; according to Lowne these sclerites are not 

 recognisable in the Blow^-fiy maggot till after the second 

 moult, so that their absence in the young warble-maggot 

 might have been expected." 



Fig. 4. — Calliphora sp., mature larva, mouth armature, side view, x 40. 



Ji, mouth hook ; ph. s. pharyngeal sclerite ; p.s. parastomal sclerite ; 

 h.s. hypostomal sclerite. 



The paired parastomal sclerites which are present in most 

 muscoid larvae, that of the blue bottle, Calliphora (Fig. 4, 

 p. s.) for example are well represented in all the larval 

 stages of Hypoderma by the central spine (Figs, i, 2, 3 p. s.) 

 previously mentioned. The mouth-parts of the second 

 larval stage as also of the newly discovered third stage do 

 not differ noticeably from those of the first stage except 

 that in respect of size they are somewhat smaller. It is 

 after the third moult that considerable modification is 



A 3 



