94 * Psyche [June 
MIGRATING LARVZ OF SCIARA CONGREGATA 
JOHANNSEN. 
By Grorce G. BECKER, 
Agricultural Experiment Station, Fayetteville, Arkansas. 
The species of Sciara which Prof. Johannsen describes in this 
issue of Psycue, first came under my observation on July 6, 1912, 
when I noticed an army of the larve in a chain about five feet 
long and three inches wide at its greatest width. The chain of 
larvee 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 larve. 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 larvee from the rear came up and traveled 
over their fellows in front of them. It was noticed that the larvee 
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 larvee 
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 larve from above. These 
larvee, 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 larvee 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 larve left a 
sort of trail in their wake somewhat similar to the track passed 
over by a snake. 
