HUNGERFORD: AQUATIC HEMIPTERA. 181 
2 
3 
2 
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which they present concerning form and function. The following species 
_ were studied and figured: WN. lutea, N. raleighi, N. undulata, N. varia- 
bilis, N. insulata, N. glauca, N. mexicana, N shooterii, N irrorata, N. 
uhleri, and N. indica. Sufficient material of N. undulata, N. variabilis; 
_ N. insulata and N. irrorata were examined to indicate that the ovipositors 
of these may possess specific differences. Kirkaldy long ago gave up the 
_ idea of distinguishing the males by their genetalia, but it would be worth 
_ while to look into this matter again. 
; N. glauca, N. lutea, N. irrorata have long ovipositors and place their 
eggs in plant tissues. The others merely affix them to the surface, at- 
_ taching them there by means of a colorless, water-proof glue. See plates 
- XIX, XXI and XXII with accompanying legends. 
3 Migrations. These insects habitually fly from their winter quarters 
_to their breeding grounds in spring, as has been noted long ago. There 
are some very interesting notes on the migration of back-swimmers, one 
so curious that it is reproduced in substance here: 
Y “In evening twilight of a pleasant September day, 1846, Sir Geo. 
_ Simpson encamped for the night, on his route from Red river to the head- 
_ waters of the Mississippi, in the vicinity of latitude 48° north and longi- 
tude 95° or 96° west. While supper was preparing he perceived some- 
thing falling on his hat like drops of rain; and as there were no clouds 
to be seen, presumed that it could not be rain. On looking on the ground 
near the fire he saw that the falling objects were winged insects, which, 
although unable to fly, had life and motion. The number rapidly in- 
creased so as to give great annoyance, and continued till the ground was 
covered by the shower. On the following morning Sir George found that 
_this shower extended from 25 to 30 miles in the direction he was travel- 
‘ing. No information as to its extent other directions. It was ob- 
served that soon after the shower the weather changed from warm to 
cold. It is therefore probable that the whole of this immense swarm of 
insects encountered the cold current, and were paralyzed and precipi- 
tated thereby. They all died soon ‘after falling. In no instance were they 
seen to revive after coming into a warmer atmosphere.’—Amer. Journal 
“of Science and Arts for November, 1847. 
The above appeared in American Journal of Science and Arts for 
November, 1847, by Prof. Forrest Shephard. It relates to the same mi- 
gration that was mentioned by the writer in his quotation from S. G. 
Simpson in a former paper. 
; Means of Defense. All collectors, from Frisch, 1728, to present day, 
testify to the stinging propensities of uncautiously handled back-swim- 
“mers. If handled carelessly, they pierce one with the stylets of their 
beak, the burning, painful sensation of which may last for some time. 
sDoetors Riley and Johannsen considered it of sufficient importance to 
figure the salivary apparatus of Notonecta in their “Hand Book of 
“Medical Entomology.” 
_ Some species, N. variabilis, for instance, secrete; when handled, a 
milky fluid which oozes from the sides of the thorax beneath the wings 
and at the base of the so-called coxal plates. This fluid reminds one of 
a similar secretion of Gyrinids. 
NOTA cage 
__ Enemies. Predators as they are, their lives are in constant peril. 
The newly hatched are eaten by their older brothers. Woe betide the 
