Sept., I9I2.] Matheson : Haliplid.e of North America. 189 



while the terminal claw bears a few setae (Fig. 25). This makes 

 an ideal arrangement for grasping and holding filamentous algje. 



Feeding Habits of the Larva:. — Although Schiodte has given us 

 much detailed information regarding the structural characters of these 

 larvje he made no observations on their habits. His detailed studies 

 on the larval mouth parts led many to conclude that they are carnivor- 

 ous. What was my surprise when I found what had always been con- 

 sidered carnivorous species eagerly devouring the alg?e amongst 

 which they were living! My chief fear in attempting to rear these 

 larvae was the securing of a food supply. However, this difficulty 

 was quickly removed when I found the larvae eagerly devouring fila- 

 mentous algae. I have previously described the remarkable modi- 

 fications of the first pair of legs. I have also described the sharply 

 curved mandibles each pierced by a small tube, similar to that found 

 in the larvae of the Dytiscidae. These larvae feed exclusively on 

 filamentous algae, Spirogyra, Zygenma, Muogeotia. etc. It is a re- 

 markable sight to see one of the long spined larvae of Peltodytes 

 eagerly grasp a strand of algae and by means of its forelegs push it 

 backwards like a sailor hand over hand until it reaches a broken end. 

 Then by puncturing the cell wall with its sharp mandibles the larva 

 sucks the contents into its mouth. By means of a hand lens or low 

 power of the microscope one can easily observe the chloroplasts pass 

 through the hollow mandibles. The front legs are used to hold and 

 push the filament forward as fast as the contents are removed by the 

 mandibles. When the larva finishes the strand it will again pass the 

 alga backwards hand over hand or rather foot over foot, while the 

 mandibles secure any of the contents not previously obtained. 



I did not observe any of the larvae studied to attack any living 

 form, though numerous small Entomostraca were constantly present 

 in my aquaria. 



Adaptations of the Larvcc. — The adaptations of these larvae to their 

 aquatic environment are found in the structure of the mouth parts, 

 the legs, and the manner of securing an air supply. The mouth parts 

 in conjunction with the prothoracic legs seem to be especially fitted 

 for the obtaining and handling a food supply. The meso- and meta- 

 thoracic legs seem to be particularly adapted for walking over fila- 

 mentous algae. They are long and terminate in a single claw which 

 bears a short, fine, basal spine. But the most remarkable adaptation 



