Sept., I9I2.] Matheson : Haliplid^e of North America. 187 



The Egg. — The egg is pure white in color, oval. Length .365 mm.; 

 width .22 mm. In my aquaria these eggs hatched in ten to twelve 

 days after oviposition. 



First Instar. — Length including caudal setae, 2.5 mm. ; caudal setae- 

 .4 mm. The larva consists of thirteen segments, exclusive of the 

 head. Each segment, except the last, with several two-jointed spines. 

 The last segment is prolonged into two long spines, each terminating 

 in a short seta. This stage occupies about nine days. 



Fig. C. Lateral view of head of larva of H. ritficoUis. 



Second Instar. — Owing to the small number of larvae in my aquaria 

 I did not reserve any specimens of this instar for detailed description. 

 This stage lasts from eleven to twelve days. 



Third Instar. The Mature Larva (Fig. 36). — Length, including 

 the anal appendages, 9 mm. The head is strongly chitinized, some- 

 what depressed. Ocelli, six, arranged as- shown in figure C. An- 

 tennae four-jointed, with a short terminal spine. The last segment 

 consists of two closely approximated pieces. 



Excluding the head the larva consists of three thoracic and ten 

 abdominal segments. The legs, except the first pair, are fitted for 

 walking. The last abdominal segment is prolonged, ending in two 

 unjointed spines. Each spine ends in a single long seta. Length of 

 last seginent, exclusive of spines, 1.2 mm., spines, .38 mm. Each 

 segment, except the last, with two dorsal chitinous plates. These 

 plates meet on the mid-dorsal line. Those of the eighth and ninth 

 abdominal segment are each fused into one. These plates are closely 

 set with many, short, stout spines. The ventral surface of each 

 segment is more or less chitinized and provided with numerous short, 

 stout spines. 



Spiracles are present on the meso- and meta-thoracic and the 

 first seven abdominal segments. The spiracles are located in the 

 pleura between the lateral and ventral chitinous areas of each segment. 



