248 NATURAL HISTORY OF AQUATIC INSECTS CH. 



small plates of mica, in the hope that a transparent 

 case might be obtained. This expectation was 

 perfectly realised. The Caddis-worm made a shapely 

 and sufficiently transparent case of mica, and per- 

 mitted the following observations to be made, which 

 I quote from Mr. Taylor's notes: — ^ 



" When Phryganea grandis is at rest it is retracted 

 within its sheath, the tips of the legs alone projecting 

 from the opening. The front part of the animal as 

 far back as the third abdominal segment is arched, 

 and comes close up to the top of the sheath, while 

 the rest of the body reclines on the floor to which the 

 hooks at the tail end are firmly attached. The 

 animal is not however still, but at intervals waves its 

 body up and down, causing a stream of water to flow 

 through the case from the head end. The undulations 

 begin at the second abdominal segment, and pass 

 backwards to the tail end just as in a piece of string 

 which is fixed at one end and waved up and down at 

 the other. The rest of the body is kept steady so 

 that the stream of water has a free admission. This 

 seems to be effected by the lateral processes of the 

 first abdominal segment, which can be pressed against 

 the sides of the case and kept from slipping by the 

 spines which cover their points. The median tubercle 

 is different in form and structure from the lateral 

 ones, and can be protruded or retracted with great 



ease." 



^ The trial succeeded most readily with Limnophilus rhoni- 

 bicus and an undetermined Caddis-worm. Phryganea grandis 

 was very reluctant to cover its body with mica, and only did so 

 after long exposure. 



