THE CANADIAN ENTOMOLOGIST 131 



flies, midges and caddis-flies, which gather in inconceivably vast 

 numbers, in floating felted mats, that are sometimes an inch or 

 two in thickness, and square rods in area. Every cubic inch of 

 this material represents thousands of specimens. When with shift 

 of wind and rising of waves these mats are cast upon the pier, 

 they cover the planking with a plaster-like coating of ashen-gray 

 hue. There is no place where flotsam can accumulate when the 

 wind blows parallel with the piers, or when the waves break over 

 them. 



During the month of August, 1906, there was but one period 

 of abundance of insect drift upon the beach, — a period of three 

 days, the 22-24th inclusive, while the wind was E.-N.E.,and follow- 

 ing upon warm weather with westerly winds. There were scanty 

 accumulations also on the 1st, 2nd, 6th, 8th, 10th, 25th, 26th, 27th 

 and 28th, always accompanying an easterly wind. Sometimes the 

 drift was a thin line of nearly pure insect remains, scarcely discover- 

 able as a tracing along the sand at the farthest reach of the waves, 

 as on the 1st; sometimes it was a conspicuous line of trash, with 

 insects scattered thinly through the trash, as on the 22nd. On 

 only twelve days of the twenty-four recorded was there any dis- 

 coverable deposition of insects at the drift-line. 



These regular observations supplement earlier more casual 

 ones, and confirm certain opinions as to the occurrence of the drift 

 upon the shore of Lake Michigan as follows: 



1. Floating insects can be deposited at the drift-line only 

 when the waves are running shoreward. The wind is, of course, 

 the actuating cause of their transportation by water. The waves 

 follow the wind, but do not quite keep up with its changes. In my 

 notes I find three entries that bear directly upon this: — 



"6th Aug.: wind blowing strongly from eastward (it had 

 blown from the west the preceding day). I saw the drift begin to 

 come ashore at close to 7 a.m., bringing in at first many live Rhyn- 

 chophora." 



"22nd Aug.: wind shifted inshore (from N.W.) in afternoon 

 and drift began to appear in the evening. No flotsam; waves too 

 rough." 



"27th Aug.: wind N.-N.W. on land, but waves still running 

 in strongly from N.E.; many grasshoppers." 



