1916] Biology of A quatic Lepidoptera 



163 



edges; and (4) ragged leaves and fragments of leaves with very 

 irregular edges but no holes of any sort. 



The results of these experiments were as follows: 



(1) Most of the females tested with entire, unpunctured leaves delayed 



oviposition until the second or third night and then laid diminutive 

 egg masses on the lower surface of the leaf near the margin, particularly 

 m the region of the leaf sinus. a ' ^ y 



(2) Egg masses were deposited around artificial incisions and punctures of 



various kinds and shapes. 



(3) Apparently, the dimensions of artificial punctures and incisions played 



u °^ "° P^^* ^" determining the location of egg masses 



(4) In the absence of leaf punctures, egg masses were deposited near the edges 



of smooth-cut portions of leaves, on the lower surface; also about the 

 irregular edges of ragged and mutilated leaves. 



It is evident from field observations and the above-described 

 experiments that the female of N. maculalis has a distinct pref- 

 erence for the egg holes of Donacia in oviposition and that when 

 present they are constantly utiHzed. However, in spite of the 

 fact that, in the Douglas Lake region, the eggs are normally and 

 constantly placed as above described, it is evident from the 

 experiments that the dependence upon the presence of Donacia 

 egg holes is not absolute and it seems fair to assume that in case 

 N. maculalis occurs in a locality where Donacia ^gg holes or 

 similar leaf punctures are absent, &gg masses would be deposited' 

 about the leaf margins of the food plant. Observations on the 

 egg-laying habits of N. maculalis in other parts of the continent 

 would be of interest in this connection. This moth is widely 

 distributed, having been reported from locaHties ranging from 

 the Gulf States to Central Canada. Species of Donacia are said 

 to occur in all parts of the United States and Canada and, 

 although not all of them lay their eggs around circular holes in 

 water-lily leaves, it appears that at least one of the rather widely 

 distributed species does have this habit. The extent of this 

 egg-laying interrelation of the two groups of insects is a problem 

 for the future. 



Description.— T\iQ eggs are elliptical, smooth, slightly com- 

 pressed, and constant in size. When first hatched, the max- 

 imum dimensions are 0.396 mm. and 0.549 mm. The development 

 of the Qgg is accompanied by an increase in size so that just 

 before hatching the dimensions are 0.450 mm. and 0.648 mm. 

 Of the considerable number of measurements made, none 

 varied more than 0.03 mm. and even this variation was excep- 

 tional. It will be noticed that measurements of the egg made 



