DK. CHILD'S LETTER. 
93 
All my records and recollections say they rise to depart between 9 a. m. and 12 m., 
and never unless there is a swarm in motion overhead. 
2 a. June 13 to 15, 1868. — Towards northwest on a southeast wind. 
1869, June 20. — After a four days' southerly wind, they came down largely on a north 
wind. 
1875, June 13 to 22. — The air was full of them every day, the wind generally from 
south or southeast. The locusts weut with it ; two short changes to northeast brought 
them to the ground. 
June 24. — During the forenoon the wind was light from the north, and locusts with 
it (a rare case). At noon full calm, and progress stopped. They circled round and 
round, and many came down. 
25th to 28th. — Wind southeast. Locusts on it to northwest. 
June 14 and 15, 1876. — To the southward on northerly winds. 
August 10. — No wind and no general course. 
August 24 and 25. — Northwest and northeast winds brought a few. 
On the above times the winds were generally light, from five to ten miles per hour. 
The weather fair, of course, where the locusts were visible, for they are invisible in 
cloudy weather. 
2 6. The temperature at the time of rising has ranged from 70° to 90°. Cold or cool 
weather renders them sluggish. 
2 c. The direction always corresponds with the flocks above, of which I have spoken 
above. I have rarely seen a large number rise at once. The lower air will be very 
full of -them, but at least four- fifths of them rise, take long horizontal flights, but 
seemingly unable to rise, come to the ground again. I presume they have to make 
several attempts before they succeed. 
August 24, 1876. — I first noticed them. I know nothing of any marching or travel- 
ing except as they march across a field of grain or other food and leave a bare plain 
behind them. When on the wing I am inclined to think they fly all night. Their 
movement must be regulated largely by the wind they are on, and this they out-travel, 
according to my observation. 
Yesterday, July 22, about noon, I noticed they were passing over in very large num- 
bers ; a fight southerly wind blew them northward. I gave my entire attention to 
them, and watched them, assisted with a spyglass. The swarm was of great depth, 
at least one-quarter mile ; how wide I had no means of determining. Through some 
peculiarity of the atmosphere, probably aided by a lower flight than usual (the bar- 
ometer indicated from 30.019 to 30.062 inches jiressure) I kept them in view until after 
7 p. m. with no perceptible diminution of numbers. Careful observations in the even- 
ing, and again this morning, show not a single one on the ground. 
At 8.30 this morning I succeeded in getting sight of them again overhead, and as 
the sun rose higher developed numbers about the same as yesterday. (Query: was the 
flight continuous through the night?) 
For several years I have observed the locust, and have seen no exception to the gen- 
eral rule that it is very sluggish in the cool of the morning, i. e., on the earth. It does 
not leave its perch, roost, or bed until the air is warmed up from 8 to 10 a. m. Sup- 
posing this swarm had descended somewhere ; it must have literally more than covered 
the ground ; yet, in violation of their general habit of late rising, here they r are at 
8| a. m. in regular flight overhead. The thermometer last night was at 68°, this morn- 
ing at 7 a. m. at 64°. A minimum thermometer fell during the night to 55°, altogether 
too cool for them to have risen from the earth to recommence their flight this morning. 
But, on the other side, if cold renders the locust sluggish, how does it succeed in keep- 
ing on its way in the upper strata of air, which are much colder than that on the earth ? 
Does its action develop enough heat to enable it to keep up its flight? When met by 
opposing winds I have seen them come down in large numbers, but by common con- 
sent to descend en masse I have no knowledge of it. I see no way to avoid the conclu- 
clusion that they fly all night. 
A. L. CHILD, M. D. 
