CORRESPONDENCE. 



745 



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 Sun- 

 day, 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 snow- 

 storm, 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 depos- 

 iting their eggs. 



We would refer, in conclusion, to one 

 feature of their habits again. These fish, 

 at the commencement of winter, by burrow- 

 ing 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 ap- 

 proach of spring, they arrive, synchronously 

 with the maturing of the ova in the females, 

 and milt in the males, and, after thus re- 

 covering their wonted activity — say in Feb- 

 ruary — 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 re- 

 ferred 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 glisten- 

 ing frost, we found the plainly-colored, di- 

 minutive mud-minnows hidden among the 

 pebbles and sandy ridges of the brook-bed. 

 Charles C. Abbott, M. D. 



Tkenton, N. J., March 2, 1874. 



ANIMAL MIGEATIONS. 

 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 house- 

 fly, 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 bur- 

 rows in the ground for transformation. 

 Sometimes four of these larvae will be found 

 in one locust. I first noticed this in the 

 summer of 1871. In 18*72, 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 un- 

 usually fine opportunity to observe the lo- 

 custs, as they hatched in incredible num- 

 bers upon my farm, and devoured my crops. 

 During the whole summer the fly left the 

 locusts no quiet, but drove them to most des- 

 perate 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 " Entomol- 

 ogy." If comparatively new, there is hope 

 that it will work the destruction of the lo- 

 custs. I also believe the latter can be read- 

 ily destroyed by the combined efforts of 

 man, as they hatch in exceedingly small 

 areas. 



