26 



Mr. B. F. Oumniiims on the Head and 



the group occurs iu F. gravenhofstliy McLachhin (8) 

 remarks that the ''Australian genus PledroUirsus has tlie 

 parts of the mouth moditieJ in an extraordinary manner, 

 forming a beak or rostrum . . . ." How inadequate and 

 .inaccurate the terms " beak " or " rostrum " are will be seen 

 presently. 



Head. — This is of a shape and character unusual in the 

 order. In Phryganea, for example, it is more or less in the 

 shape of a wedge, the base of the wedge being formed by the 

 epicranium and the mouth-parts running down and gradu- 

 ating in size to form the narrow end. In Phryganea, too, 



Fis. 3. 



TentoriuQi of Pledrotarsus gravenhorstii (sides and roof of skull cut 



away), 



E, eye ; O. occiput ; CB, crossbar ; BB, dorsal branch ; 

 GR^ galar region. 



and in most Trichoptera the whole of the giilar region is 

 membranous or very thinly chitinized, so that the base of the 

 skull is incomplete beneath. On either side of this soft gular 

 region the genae extend downwards as two triangular flaps, 



