160 Annals Entomological Society of America [Vol. IX, 



Nymphula maculalis Clemens. 



Nymphula maculalis occurred in some abundance in the 

 immediate vicinity of the yellow water-lily beds and the writer 

 was able to observe the development of this species, both in the 

 field and in the aquaria, from the egg to the adult several times 

 during the five successive summers, thus establishing the 

 identity of the following described immature stages. 



The Egg (PI. VII, Fig. 5). 



The eggs were first described by Forbes ('10, p. 221) as 

 follows: "Eggs were laid in captivity, but not in a regular 

 egg-mass. They were oval and flattened, .65 by .5 mm., and 

 had no decided longitudinal ridge. Duration of stage about 

 ten days." This meager description, which seems to be the 

 only one that has been published, contains no hint of the very 

 interesting method of deposition under natural conditions. 

 The writer made a careful study of this part of the life history 

 and the results will be given in some detail. 



Place and Method of Deposition. — Eggs were found only on 

 the yellow water-lily, Nymphcea americana (Provancher) Miller 

 & Standley. Other aquatic and semi-aquatic plants growing in 

 the vicinity of the yellow water-lily beds were examined care- 

 fully but no eggs were found on them. They are laid on the 

 lower side of the floating water-lily leaf and are thus con- 

 stantly submerged. 



■Oviposition is associated in a very interesting and unique 

 way with the deposition of the eggs of another aquatic insect. 

 During the past five summers, the writer found about one hun- 

 dred egg masses of N. maculalis in the field and, without excep- 

 tion, all were deposited in the manner to be described. A 

 species of chrysomelid beetle (Donacia sp.), which occurs in 

 considerable abundance about the water-lily beds of Douglas 

 Lake, deposits its eggs on the lower surface of the leaves of the 

 yellow water-lily in a very characteristic way. The female cuts 

 a circular hole, 4-6 mm. in diameter, through the leaf and then, 

 by means of a long ovipositor, lays two concentric rows of white, 

 elliptical eggs around the margin on the lower surface. These 

 concentric rows are very rarely complete, so that there may be 

 two or more groups of eggs around the hole with varying inter- 

 vening spaces. The interesting thing is the fact that the female 



