186 THE UNIVERSITY SCIENCE BULLETIN. 
nymphs are clear white, with red eyes as seen from above. The limbs 
are transparent as is the abdomen also. The antennae, claws and hairs 
are dark. In ten minutes the limbs begin to get smoky. When they have 
hatched within the water the guard hairs of the abdomen hang limp. 
The insect seems water-logged. It comes up to the surface head up, and 
repeatedly sinks back to the bottom exhausted. Finally a stronger effort 
than before enables it to hook the front claws into the film, then after 
a sudden turn it goes down with an air bubble imprisoned beneath the 
abdominal guard hairs. 
In a battery jar the adults were active for a long time. The adults 
liked to cling beneath the rubbish and Moneywort tangle. They were 
fed the nymphs of damsel flies and Corixids. On June 25 the eggs were 
present in all stages from those showing red eye spots to those newly 
laid. The last of the three backswimmers was alive and active July 9 
and the notes fail to show her fate. 
This account shows that the egg laying can be carried out under 
laboratory conditions and that it lasts from early May to the end of 
June at least. 
Fecundity. On March 26 a female was dissected and found to con- 
tain 252 ova, several of which were nearly ready for laying. The period 
of oviposition lasts from early spring until into June, in the laboratory 
not more than a half-dozen eggs being laid on any one date. 
Longevity. Adults certainly are capable of living at least a year. 
There is evidence to indicate that adults of the previous year may oc- 
casionally live over until the new generation comes on in July. They 
are few, however. If cared for in the laboratory they might exist well 
through the second season. 
Food Habits. Like others of their kind, they are predators. In their 
first stages in the laboratory they were given Ostracods and other small 
Entomostraca, also Corixid nymphs. By the time they reach the third 
instar they can master adult corixids of Palmocorixa genus (when they 
can catch them.) As elsewhere noted, the adults show discrimination. 
They caught but immediately liberated some pink Phyllopods offered 
them. 
Behavior. The late instars are given to spending considerable time at 
the surface, like the N. undulata. The adults, however, are not so in 
evidence and come out in the sweepings of the net as pleasant surprises 
to add zest to the activity of the amateur collector. 
Description of Stages. 
Egg. 
Size. Newly-laid egg, length, 1.51 mm.; diameter, .572 mm. 
Shape. Elongate oval, but shorter in proportion to its length than N. 
variabilis, N. undulata or N. insulata. In lateral view the anterior end of 
the egg is seen to slope back from the base of the micropyle more than 
the others. (See pl. XIX, fig. 6.) It is this portion of the egg that is 
exposed as it lies in the plant stem. 
* Frisch, 1728, said that the young stages of N. glauca were more often seen than 
the adults. 
