1922. Phibbs. — The Larval Mouth-Hooks of Hypoderma. 29 



The fused hypostomal sclerites (h. s.) have also become 

 more massive ; they are much shorter and no longer project 

 over the pharyngeal sclerites. The actual mouth hooks 

 have entirely disappeared though the central spine {p. s.) 

 is slightly larger in this than in the fourth stage. 



In connection with this absence of the mouth-hooks in 

 the fully-grown larva N. Joly (3) writing in 1846, says : — 

 " Indcpendament des nombreux caracteres qui peuvent 

 deja nous servir a differencicr la larve de 1' Hypoderma 

 bovis d'avec les larves gastricoles ou cavicoles il en existe 

 un autre plus essentiel peut-etre : je veux parler de 

 I'absence des crochets mandibulaires. Ici, en effet, la 



ps 



hs 



Fig. 6. — H. bovis, fifth- stage (mature) larva, mouth armature, ventral 

 new, X 50. 



ph. s. pharyngeal sclerite ; p.s. parastomal sclerites ; h.s. hypostomal 

 sclerites ; g. gullet ; s.d. salivary duct. 



bouche consist e en une simple ouverture, extremement 

 petite, et tres-difficile a mettre en evidence chez I'insecte 

 vivant." 



There has been some doubt expressed as to the accuracy 

 of the statement that there are no mouth-hooks in the 



