G. G. Becker.
Migrating Larvae of Sciara congregata Johannsen.
Psyche 21:94, 1914.

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94 Psyche [June
MIGRATING LARVA% OF SCIARA CONGREGATA
JOHANNSEN.
BY GEORGE G. BECKER?
Agricultural Experiment Station? Fayette~ille~ Arkansas. The species of Sciara which Prof. Johannsen describes in this issue of PSYCHE^ first came under my observation on July 6? 191,!& when I noticed an army of the larvz in a chain about five feet long and three inches wide &t its greatest width. The chain Gf larvz was widest at about the middle and tapered toward each end.
The general appearance of the army was that of a dead snake and I was about to pass by it when closer observation showed that it consisted of a migrating mass of larvce. The chain was moving very slowly at a rate of probably not more than a few inches per minute.
In general the movement of the army suggested a sort of flow- ing motion in which the larva? from the rear came up and traveled over their fellows in front of them. It was noticed that the larvce on the top made much better progress than those below, This would naturally be the case since the individuals on the top de- pended upon those beneath them for purchase. Since the larvce must have been piled up about eight deep in the middle of the procession it would seem that those next to the ground would be unable to make much progress, and that they would therefore have to wait until those to the rear had passed over them before they could gain any headway. It was thus noticed that the ad- vance of the chain was made by the Iarvz from above. These larva?? naturally, made more rapid progress than those beneath them? and they no sooner gained the ground in front of the chain than they were followed and covered by the great mass of migrat- ing larvce coming from behind. Probably they did not emerge again until most of the chain had passed over them. The locomotion of the individual larva was accomplished by a series of intermittent? jerky? flowing movements by which the larva glided over those beneath it. These migrating larva? left a sort of trail in their wake somewhat similar to the track passed over by a snake.




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