OF MAXILLUL^E IN THE ORDERS OF INSECTS. 



447 



bypopharynx in Hepialus humuli. Although the family to which this species 

 belongs is in many respects primitive the bypopharynx is apparently con- 

 siderably specialised. It does not seem to afford any clue to the original 

 form of the maxillulae iu Lepidopterous larvse. The whole of the mouth- 

 floor is remarkably soft, rounded and membranous, and the areas of chitin- 

 i/.ation very small. A pair of lateral membranous protuberances were too 

 indefinite in character to be homologised with maxillulse. 



TBICHOPTEllA. 



The bypopharynx has been investigated in eruciform larva? of Phryganea 

 and Limnophilidse and in the eampodeiform R/iyacoptiila and Hydropsy die. 

 It was found in most cases to bear a general resemblance to that of Lepido- 

 ptera. Its dorsal wall, forming the floor of the mouth, is produced distally to 



lihyacophila sp. Labium and bypopharynx, dorsal aspect. X 250. a.m. Mental 

 arm. h. Hypophavynx. l.p. Labial palp. m. Maxillular lobe. p. Plate 

 supporting' outer wall of lobe. s.p. Spinneret. 



form a conical spinneret. Laterally its walls are continuous with those of 

 the labium. With the exception of Phryganea all the examples investigated 

 were found to be constructed on a common plan, which can be best described 

 by a consideration of the condition in a species referable to the genus 

 Rliyacopliila. 



