\ 



ADJUSTMENT OF ORGANISMS TO ENVIRONMENT 419 



( Length in millimetres (most easily and quickly 

 Size -{ taken with a small caliper rule). 



Weight in grams (weigh each species on a deli- 

 cate balance; put beetles in envelopes made of 

 filter paper, which will take up the water, a number 

 at a time of the smaller species ; weigh in envelope ; 

 weigh envelope alone; deduct; divide remainder 

 by number of beetles weighed; quotient should be 

 the average weight) . 



Strokes per second. (Set a metronome 

 beating half seconds and count). 



Strokes per length of body (measure of 

 the efficiency of the individual stroke). 

 Speed per second*. 

 Swimming (a? determined above). 

 Walking (judge this not by speed alone, 

 but by ability to get up on feet and walk, 

 using the joints of legs and feet). 

 Jumping. 

 Taking flight. 

 Dodging. 



The record of this study will be contained in the completed 

 table, which should show clearly the great differences in 

 the powers of these beetles, that underlie their super- 

 ficial similarity. 



Swimming 



Relative 

 excellence t 



*Place the beetles, one species at a time, in a broad, shallow 

 dish of water, and lay a few pieces of soft wire of measured lengths 

 (5, 10 and 20 cm.) on the bottom. With the metronome beating 

 half seconds, watch the beetles as they swim about, and judge by 

 the time it takes them to pass given lengths of wire. 



t Expressed numerically: the best swimmer as i, second best 2, 

 etc., written in the columns. All these but the last (which is best 

 seen in the water) may be easily determined by placing beetle of 

 all the species used together on a sheet of paper spread out on as 

 table before a window. Place them on the side remote from the 

 source of light, and they will travel toward the light according to 

 their several abilities, walking, jumping and flying. 



