June, '08] ENTOMOLOGICAL NEWS. 283 



plate, and often the anterior annnlus of the first segment also 

 bears a plate. 



The plates at the posterior and anterior ends of the body 

 are much the larger. The first and usually the second pro- 

 thoracic and first mesothoracic plates are so cleft from behind 

 along the median line as to form two plates placed side by side. 

 Besides these dorsal plates the body is well armed with very 

 short bristling hairs and a few long ones. The posterioi an- 

 nulus of each abdominal segment bears two pairs of long bris- 

 tling hairs on its dorsal and ventral surfaces and one or more 

 similar hairs on its lateral margin. The anterior annulus of 

 the thoracic segments bears similar hairs. These hairs are 

 mounted upon low papillae and are usually curved rather than 

 straight. One or both pairs on the dorsal surface of the 

 posterior segments may be mounted upon the dorsal plates. 



The larvae possess the prothoracic air nipples, as in the other 

 forms. So far as I have been able to determine, these are 

 never used for respiration, unless perhaps when the larvae leave 

 the water and crawl up the sides of the jar or along on the 

 straws and weeds which extend above the water. At this time 

 they have only a thin film of water around them and the four 

 small projections bearing the cilia which protect the posterior 

 breathing pores are usually retracted so that these breathing 

 pores are closed and at such times air may be taken through 

 the thoracic air nipples. 



While feeding and while in the water respiration is carried 

 on entirely through the posterior spiracles. It is interesting 

 to watch this operation. After the larva has been at the 

 bottom of the jar feeding for a while, a small bubble of gas 

 will begin to form at the tip of the breathing tube. This is 

 continued until the bubble has reached a considerable size, when 

 the larva stops feeding, lets go all hold, and rises to the sur- 

 face much as an aeronaut. On reaching the surface the bub- 

 ble bursts, the cilia around the spiracles spread out and hold 

 the larva in place until a new supply is drawn into the tracheal 

 system, when the cilia are retracted and the weight of the body 

 of the larva carries it to the bottom of the jar again, where 

 it continues to feed. The fresh air in the tracheal system is 



