190 THE UNIVERSITY SCIENCE BULLETIN. 



Biology of Notonecta undulata Say. 



Habitat. Notonecta undulata, besides being the most widely-dis- 

 tributed form, seems to be able to adapt itself to a wider range of cir- 

 cumstances than most of the others. The writer has taken it in clear 

 spring-fed pools in New York and in the stagnant scum-covered waters 

 of muddy ponds in Kansas. Uhler, 1876, says "it inhabits the foulest 

 pools, in dirty slush and slimy ponds it revels in full enjoyment of the 

 filth." 



Barber, 1913, in a popular paper on aquatic Hemiptera, makes a 

 similar reference to its habitat. Thus it may be noted to be less sensitive 

 than many others of its genus to its environment. When the small bodies 

 of water recede during the prolonged period of dry weather, which we 

 sometimes have in late summer in Kansas, it is among the last to take 

 wing to more favorable situations, a fact which is not to be accounted 

 for on the basis of weak powers of flight, for it does on occasion fly very 

 well, as appears to have been noted for the European forms at an early 

 date. Aldrovandus spoke of them as amphibious bees and Swammerdam, 

 at the^ close of his discussion of the Notonectse, a name applied to them 

 by Mouffet, 1634, makes the following interesting remark in regard 

 to the migration of water bugs : "As all the insects hitherto enumerated 

 have wings, some of them flying in the daytime and others at night, it is 

 easy to conceive that they may be very speedily generated in all standing 

 waters." 



In the first warm days of spring, the writer has observed them com- 

 ing by the dozens and alighting in a small road-side pool. Thus their 

 range, which was restricted by the drouth of the previous fall, was again 

 extended to the many favorable pools of spring and early summer. There 

 are several records of Corixid migrations in this country but only one, so 

 far as the writer knows, for Notonecta. In September, 1846, near the 

 head waters of the Mississippi, S. G. Simpson reported a swarm of "iV. 

 glauca," which extended over 25 or 35 miles. This species, if a Noto- 

 nectid at all, was doubtless the common N. undulata. 



Hibernation. The adults may be taken any time during the winter 

 when the waters are open enough to permit collecting. They pass the 

 coldest portion of the year in the mud or among the rubbish and dead 

 leaves in the pool. They can even spend as long as six weeks in damp 

 piles of dead sticks, so it does not necessarily follow that they perish be- 

 cause pools diminish during weather when they are but sluggishly active. 



Mating. Mating takes place with the first warm days of spring, and 

 as with other water insects takes place beneath the surface and lasts for 

 some time. 



Oviposition. The eggs are glued to supporting vegetation, sticks, 

 posts, rocks, tin cans, or even to snail shells that lie submerged. A 

 very satisfactory idea of the eggs may be obtained by viewing the 

 photograph on plate XXI. 



Incubation. The egg stage varies from five days to two weeks, de- 

 pending upon the temperature. 



