2 9 



view, and the fat sacs often increase in size. The Malpighian tubules 

 become swollen to twice their original diameter but remain the same 

 length as before. Rudimentary sexual organs become more or less 

 visible in the last two segments of the body. The rudiments of the 

 imaginal organs are also clearly seen in the thorax, \vhere the greatest 

 changes are taking place, and they account for the swollen appearance 

 of the anterior segments. 



I may mention here that many larvae are infested by parasites 

 (nematoid-worms ?) which coil themselves up in the body cavity. They 

 are often between two and three times the length of the larva they 

 are feeding upon, and one-third the diameter. Between 5 and 10% 

 are thus infected. The only other parasite I have noticed is an Alga- 

 like plant found in the rectum ; it consists of strings of minute oblong 

 green cells, and some single ones attached to the walls. Similar Algae 

 are mentioned as being found in the cockroach.* 



TUBE BUILDING AND OTHER HABITS. 



Chironomus pusio makes a dark-brown mud tube composed of Tube of C. pusio. 

 rough particles carefully plastered together by saliva, but there is no 

 internal lining of silk such as is often found in the cases of Trichoptera. 

 The tube is attached for a variable length to rock or moss stem in the 

 bed of a river, but it gradually curves away from its support, so that 

 the anterior end projects freely in the water ; this end is the widest, 

 from which it gradually tapers towards the base. From the circum- 

 ference of the wider free extremity curve out at right angles to the 

 tube a number of slender arms, in the full sized specimens generally 

 from four to seven, but in the small ones often only two or three, 

 though some cases, even those belonging to the first instar, may have as 

 many as five. The arms spread outwards and forwards, and when 

 covered with a net-work of threads, form a kind of shallow cup in 

 which floating particles are entrapped to become the food of the 

 sagacious larva. The diameter of a fair-sized net is 8 mm. and the 

 tube '615 mm. The larva lives inside the tube, only coming out from 

 time to time to collect food or mend the net, and it is important to 



* MIALL & DENNY, Appendix p. 221. 



