April, 1887.] history society of Wisconsin. 133 
* 
remarkable littoral distribution. To what degree is this distribu¬ 
tion accidental, i. e. to what extent influenced by the action of the 
lake water ? What are the causes of this accidental distribution ? 
To what degree is this distribution natural ? These are the 
questions which I shall attempt to answer in the following 
paper. 
Before proceeding, however, to answer these questions, let us 
consider the extent of shore examined. My observations have 
been limited to the portions of beach north of the river-mouth, 
partly because they were more easy of access, partly because re¬ 
peated visits to the southern beach of the county failed to reveal 
any specimens. Within the city limits the improvements of the 
Chicago & North-Western R. R. have obliterated all but a small 
portion of the original shore line. This is a short but very 
broad sandy beach at the northern corner of the bay where the 
railroad leaves the lake shore. Trespassing on the shore between 
this beach and the “water works” is forbidden. The beach most 
thoroughly examined, however, begins just north of the “water 
works” and extends to White Fish Bay. It is lined on the west 
by a wall of low bluffs, sometimes covered with grassy pastures,, 
sometimes crowned with dense woods. This wall of bluffs is 
broken every now and then by ravines, worn by little streams 
which flow into the lake. The mouths of these ravines are often 
broad, and have an unusually great accumulation of drift-wood. 
This long stretch of beach is far from being regular. In places it is 
broad and sandy, more frequently it is narrow and covered with 
coarse, wave-worn pebbles. At times it is crowded with bould¬ 
ers, which project into the water and serve as a landing place for 
many insects. 
Let us first consider what I call the accidental distribution of 
the Coleoptera over this area. The waves washed up thou¬ 
sands and thousands of beetles of many genera. Had these 
any peculiarity in common ? Without exception they were all 
hying Coleoptera, The plant-eating genera endowed with the 
greatest powers of flight were the most abundantly represented. 
The greater number of species were nocturnal, though the 
Coccinellidx and Chysomelidai which were at times exceedingly 
