120 Journal New York Entomological Society. [Voi. xxv. 



(fig. 17). There is also a certain sexual dimorphism manifest in the 

 pala, or terminal segment of the foreleg. 



Laboratory Studies. 



After having discovered the source of their food supply, the glass 

 petries employed in bacteriological work were found admirably suited 

 to the needs of one wishing to study the habits and life history of 

 these boatmen. 



In order to obtain definite data on the number and length of the 

 instars, newly hatched corixids were isolated in 11 cm. petrie dishes, 

 and the dates of ecdysis recorded. 



In addition, they were reared in petries and also in large porcelain- 

 ware pie-pans, as general checks on the isolated rearings. AH of the 

 laboratory observations were accompanied by observations of the 

 general cycle in nature. 



Space does not permit the recording of the notes on all the lot 

 rearings, but two are herewith presented to suggest in a general way 

 the variation of development for the spring generation. 



Pctric F. — A petrie dish, 15 cm. in diameter, was chosen to carry 

 an entire lot through as a general control on the isolated rearings. 



Eggs were laid on a large dead cottonwood leaf in the laboratory 

 between the afternoon of March 25 and the morning of March 27. 



On April 8, two were hatched, and the remaining eggs showed 

 the red eye spots of the embryo within. The eggs continued to hatch 

 until April 14. On this day, one entered the second instar. April 

 20, the first entered the third instar, and by April 24 there were 

 several in this stage. On Friday, April 28, one passed into the 

 fourth instar, and in the next few days, the others followed it. The 

 first entered the fifth instar on May 4, and all had reached this stage 

 by May 6. The first adult, a male, appeared May 10. The last adult 

 came forth May 17. So, for this lot, we see that eggs laid about 

 March 26 gave forth adults from May 10 to May 17, a period cover- 

 ing from about 45 to 53 days, and allowing a variation of about a 

 week in the development of boatmen from a single laying. This 

 is evidence enough that the rearing should be carried out on a much 

 larger scale than is presented in this paper, in order to ascertain the 

 maximum time to be found in each period of development. 



