7 86 THE POPULAR SCIENCE MONTHLY. 



numerous dangers ; so, to avoid this, they crawl up the banks and 

 burrow into the saturated mud or soil, and at times penetrating from 

 the stream-bed, the earth or mud thrown out forming the mound, an 

 opening or door is generally left at one side or on top. Water collects in 

 the bottom of this burrow, while the upper portion is entirely free, thus 

 enabling the cray-fish to take to the water or not, as it is inclined. 

 These mounds are probably built when the streams rise, the crustaceans 

 leaving the swift current and taking to the higher ground for better 

 security. To show how a flood or over-supply of water will at cer- 

 tain times alarm these little creatures, a gentleman residing in Free- 

 port, Illinois, informed me that not many months ago they had some 

 very heavy rains, that greatly increased the volume of the little river 

 running through the town. The water gradually rose until num- 

 bers of quite large trees were submerged, and the stream was almost 

 twice its ordinary width. Such an unusual occurrence naturally at- 

 tracted considerable attention, and my informant and a number of 

 others visited the trees several times, and when the river was at the 

 highest they presented a strange appearance from a little distance. 

 Their trunks seemed to have changed color from the water up to the 

 branches, and on closer inspection it was found that they were com- 

 pletely incased with cray-fish which covered every available space, 

 crowding upward by hundreds, clinging to the bark and to each other, 

 in some spots packed one upon another four and five deep ; every mo- 

 ment added to the throng, new ones emerging from the water, while 

 those above, urged on, crept out upon the branches, and completely 

 covered them, presenting a novel and interesting sight. The animals 

 in many cases retained their positions for several days, and did not 

 seem to be affected by their stay out of water. The occasion, how- 

 ever, was taken advantage of by the people, who came with buckets 

 and brooms and swept them from the trees by hundreds, storing them 

 up for future use. The cray-fish in certain portions of the Western 

 country is a pest to the agriculturist, and the work of these little 

 creatures often greatly increases the labor and expense of breaking 

 up land, especially after the burrows or mounds have stood for many 

 years, the vegetation that has grown upon them often increasing their 

 size to mammoth proportions, comparatively speaking. Some farmers 

 consider, however, that they enrich the land by keeping it open, and 

 in many other ways, and that land with cray-fish-heaps is worth more 

 to the acre from this cause. To the man who plows his land in the 

 old-fashioned way, as many Germans yet do, the cray-fish is a hin- 

 drance and a pest. Not the least remarkable feature of the life of 

 this little creature is the fact of its living so far from open streams. 

 In many cases examined by me, no stream or brook was present, a 

 mere bog being the center of attraction. How they had wandered 

 so far from clear running water was a mystery. Scientifically, the 

 cray-fish belongs to the family Astacidce. About fifteen different 



