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Page:Popular Science Monthly Volume 4.djvu/765

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CORRESPONDENCE.

During the past month (February), the weather being most of the time mild and spring-like––the smaller frogs singing throughout the day—we watched for the first appearance of these mud-minnows, and saw them in scanty numbers, first, on Sunday, the 15th. A week later (Monday, 23d), we found but few specimens in the muddy ditches, but a vast number of females, with distended abdomens, heavy with orange-colored masses of ripe (?) ova, in the swift, clear, ice-cold waters of the hill-side brooks.

On the 25th there was a violent snowstorm, with cold northeast winds, but this did not deter the "onward" movement of the minnows. Of the specimens taken from the rivulets, at this time, none were males, and it seems probable, although we could not positively ascertain the truth, that the male fish follow the females, and either seek out the deposited ova and fertilize it (does this ever happen?), or that the females wait until the arrival of the males before depositing their eggs.

We would refer, in conclusion, to one feature of their habits again. These fish, at the commencement of winter, by burrowing deeply in the mud of the waters they frequent, avoid the decided lowering of the temperature, which they, at this season, seem unable to withstand; but, at the approach of spring, they arrive, synchronously with the maturing of the ova in the females, and milt in the males, and, after thus recovering their wonted activity—say in February—no amount of severe weather deters them from seeking out exceptionally cold waters for their spawning-beds. This was shown by the late snow-storm above referred to, after which the female minnows were still found passing up the brooks, forcing their way up miniature cascades, with all the agility of a salmon, leaping from eddy to eddy, seeking out the most distant points from their muddy summer haunts that they could reach; and here, where but little water flowed, and with the dry grass and twigs projecting from it, thickly coated with crystal ice and glistening frost, we found the plainly-colored, diminutive mud-minnows hidden among the pebbles and sandy ridges of the brook-bed.

Charles C. Abbott, M. D.
Trenton, N. J., March 2, 1874.
 

ANIMAL MIGRATIONS.

To the Editor of the Popular Science Monthly:

I believe that grasshoppers (locusts) migrate solely on account of an enemy—a dipterous insect much resembling the housefly, but larger, quicker, and grayish in color, owing to the white hairs at the edges of the articulations. This insect deposits its eggs in the upper part of the locust's abdomen, when the latter is resting on the ground, as it cannot do so when flying. Its favorite moment of attack is just as the locust alights from a flight or a hop. In a few days the larva or maggot is about a quarter of an inch in length. Soon the locust dies, when the larva eats its way out and burrows in the ground for transformation. Sometimes four of these larvæ will be found in one locust. I first noticed this in the summer of 1871. In 1872, when a flight of locusts began to arrive, the fly destroyed nearly all that came during the first two weeks, or until cool nights seemed to stop its multiplication. In 1873 I had an unusually fine opportunity to observe the locusts, as they hatched in incredible numbers upon my farm, and devoured my crops. During the whole summer the fly left the locusts no quiet, but drove them to most desperate straits to avoid the attacks; so that, as soon as the locusts acquired wings, they flew away—that is, what were left of them, for I estimate that not one in fifty escaped death. In places where the irrigating ditches prevented them from crawling forward, they were piled two and three inches deep. The ground during the cool of the day would be dotted with white maggots crawling off to find burrows. The locusts did not leave on account of famine, for there were ample fields of grain and other crops untouched; and they would sometimes abandon a field when only slightly eaten. Besides, I have seen the swarm floating all day in the air when still, and constantly alighting and arising, as hunger impelled from above, or the fly from below. I do not find this fly mentioned in Tenney's work on "Entomology." If comparatively new, there is hope that it will work the destruction of the locusts. I also believe the latter can be readily destroyed by the combined efforts of man, as they hatch in exceedingly small areas.