Sept., I9I2.] Matheson : Haliplid.e of North America. 183 



(//. riificoUis) the eggs are deposited within the dead stems of NitcUa. 

 I shall describe separately the life-history of each species studied. 



Peltodytes muticus Lee. 



The Egg. — Brownish in color, broadly oval, with faint roughened 

 markings, a small knob on the anterior end. Length .466 mm.; width 

 .254 mm. The eggs are attached to the stems of aquatic plants, par- 

 ticularly NitcUa and Chara (Fig. 33). Mating takes place in the 

 water during the early part of spring, the latter part of April and May, 

 and egg-laying begins a short time later. The average time for the 

 hatching of the eggs is about two weeks, varying of course according 

 to the weather conditions. From eggs laid on May 9, 1910, the first 

 larvae appeared on May 24. The larvae break their way out by a 

 longitudinal split through the anterior end of the tgg. 



First Instar. — Length including the caudal setse, 2 mm. ; caudal 

 setae .6 mm. Head prominent. Eyes, each of six ocelli arranged 

 in two vertical rows on a prominent chitinous projection on the lateral 

 aspect of the head. Antennae 2-segmented, with a terminal spine, the 

 proximal segment the longer. Thorax consists of three segments, 

 abdomen of nine. Each segment except the last, provided with four 

 long, jointed spines, two dorsal and two lateral. The prothoracic seg- 

 ment has four small, unjointed spines on its anterior margin. The 

 last abdominal segment possesses two long caudal setae. The caudal 

 setae are two-jointed, the second segment short and fine. The dorsal 

 and lateral setae are two-jointed, the second joint long and slender. 

 The mesothoracic dorsal spines are .6 mm. long, the first joint .2 mm. 

 The other spines average about the same length. The legs except 

 the first pair are long and fitted for walking over filamentous algae. 

 The first pair are short and modified into grasping organs. The 

 structure of the legs will be fully discussed later. Spiracles are 

 absent. 



Second Insta)'.— The first molt takes place about six days after 

 hatching. Not much change is to be noted except increase in size 

 and in the length and number of the joints of the spines covering 

 the body. Length 3.6 mm. (including the caudal spines) ; caudal 

 spines 1.5 mm. The antennae are now three jointed with a terminal 

 spine. The first joint is very short and inconspicuous. Each seg- 

 ment except the penultimate is furnished with spines as described for 



