422 THE CANADIAN ENTOMOLOGIST 



segment, the larva resembles a fully grown one in every respect. 

 The head is brownish; and when the larva attains a length of 8 mm., 

 setae have developed on it. There are a few seta? found on the 

 first thoracic segment and the blood gills now hang straight down 

 on the ventral side (Fig. 5). 



At maturity the larva measures 11 to 12 mm. in length. 

 The ventral blood gills are about 2 mm. long and longer than the 

 anal legs or any of the body segments. Just prior to pupation 

 the first and second thoracic segments become much swollen. 



Growth of LarvcE. — The young larva; emerged from eggs were 

 placed in the individual test-tubes containing about 4 or 5 cm. 

 of water. These test-tubes were placed obliquely in a dish im- 

 mersed in water for about half their length to insure uniformity 

 of temperature. They w'ere exposed to sunlight during several 

 hours of the day. Fresh food material and fresh water were added 

 from time to time. A larva which had hatched on August 11^ 

 measured .8 mm. in length. On Aug. 19, it was 4 mm.; Sept. 

 7, 6 mm.; Sept. 11, 7 to 7.5 mm.; Sept. 16, 9.5 mm. The average 

 room temperature was 18 to 19 degrees C. A second larva from 

 another egg was hatched on Aug. 15; on Sept. 11 it measured 7 

 to 7.5 mm.; Sept. 16, 11 mm.; fi\'e days later it pupated. The 

 average room temperature was the same "as above. A third, one 

 hatched on Sept. 23; on Oct. 1 it reached 1.5 mm.; Oct. 11, 6 mm.; 

 Oct. 23, 10.5 mm. The average room temperature was 10 to 11 

 degrees C. A fourth one hatched on Oct. 1 ; on Oct. 8 it measured 

 1 to 1.5 mm.; Nov. 21, 10.5 mm. The average room temperature 

 was 7 to 8 degrees C. 



The larval stage under the conditions stated lasts from 32 

 to 53 or more days. It is evident from the above that low tempera- 

 ture retards development. In the laboratory the reared larvae 

 were fed upon the finely ground leaves of Potamogetons and of 

 leaves and stems of Elodea. Under the microscope I have ob- 

 served a young larva of about 3.5 to 4 mm. long that had swallowed 

 a piece of Spirogyra which filled up almost two-thirds of its ali- 

 mentary canal. 



Larva Living Outside of Water. — The larva; of C. riparius 

 have been found to be able to live in mud for a considerable length 

 of time after the water is gone. Similarly the larvae of C. decortis 



