CADDIS-FLIES. 95 



to the species. The Helicopsyche are found only 

 in running streams. The larvae of caddis-flies are 

 chiefly vegetable feeders or have a mixed diet, while 

 some are carnivorous. The larval stage is said 

 to cover several months, but this varies with climate 

 and species of larva. It is thought that in the 

 tube-caddis, there is circulation of water through 

 the tube even when the back of the tube is partly 

 blocked up. On pupation the larva spins a silken 

 I net at each end of its case, and provides for the 

 circulation of water. 



The larva is said to attach itself to the tube by 

 j means of a pair of appendages at the end of the 

 ! abdomen, and this is thought to be aided by a pair 

 I of projections from one of the body segments. 



One of the common caddis worms (a Sericosto- 

 matid) builds a little cylindrical case which is 

 i broader at one end. (Plate 13, Fig. 9.) On ex- 

 amining with a lens, the sand grains which were 

 translucent, were seen to be beautifully cemented ; 

 the average grains were uniform in size, with 

 smaller ones fitting into smaller spaces between the 

 larger grains. On examining one of these cases 

 we found that the broader end seemed to be com- 

 pletely closed in by a *'door" made of three large 

 central grains with an outer circular row of smaller 

 ones. (Plate 13, Fig. 10.) The narrower end 

 was darker in colour and was partly closed with a 

 particle of plant tissue. Within this brittle 



case was a perfect pupa, showing wing pads and 

 long antennae. (Plate 13, Fig. 12.) One of the 

 common genera found about Sydney in pools 



