70 
THE GUIDE TO NATURE 
blamed, so I started to release him. 
Then I decided to give him a trial in 
the woodshed, where it was dark. After 
another long wait I was rewarded by 
the plaintive notes of my tiny musi- 
cian. I noticed, however, that he was 
singing much faster than his friends 
outside. This was something unusual, 
for the crickets always sing in rythmic 
unison, but I supposed it due to the ex- 
citement of his capture and the differ- 
ent environment, and that after he be- 
came accustomed to his new surround- 
ings he would get into time and tune. 
But his tempo did not change. 
I began to wonder if the temperature 
had anything to do with it. I took the 
temperature outside and counted the 
number of chirps per minute, and then 
I took the temperature of the woodshed 
and counted the number of chirps 
there. I found that in the shed it was 
seven degrees warmer than outside, and 
that my captive was chirping just 
twenty-eight more times per minute 
than were the others. This gave rise 
to the very interesting theorem that for 
every degree of rising temperature the 
chirps are increased four per minute. 
Further investigation proved this to 
be a fact, and I soon had a working 
basis for finding the temperature 
whenever the chirps could be heard. 
I found that at a temperature of seventy 
the chirps are just one hundred and 
twenty per minute. If the increase is 
four for every degree of rising tempera- 
ture the decrease must be four for every 
degree of falling temperature. By re- 
ducing our theorem to the vanishing 
point, that point will be found at a tem- 
perature of forty, though as a matter of 
fact the cricket rarely ever sings when 
the temperature is below fifty. But 
if it did its song would vanish at forty. 
Now beginning at a temperature of 
forty, if the increase for a rise of a 
degree is four for each minute, the in- 
crease must be one for each quarter of 
a minute. Therefore, from the fore- 
going data, the following axiom may 
be readily deduced: The temperature 
equals the number of chirps in fifteen sec- 
onds plus forty. This simple rule will be 
found infallible and it has afforded the 
writer a great deal of pleasure and 
amusement for many years. After the 
crickets come, in the evening I often 
say to my friends, “I think I can tell 
the temperature more nearly than any 
one present.” The challenge is usually 
taken up. After all have guessed at 
random, I take out my watch, gaze at 
it intently for fifteen seconds and an- 
nounce the correct temperature, to the 
wonder of all. Some one is sure to 
exclaim, “Well, who ever heard of tell- 
ing the temperature by a watch !” 
Perhaps the commonest night song, 
however, is that of the snowy tree 
cricket ( Oecanthus niveus). This insect 
has a day song as well as a night song, 
varying much in intensity. There is a 
distinct relation between the tempera- 
ture and the number of notes per min- 
ute. Professor Dolbear has reduced 
this to a mathematical formula. He 
says : 
Let T = temperature in degrees 
Fahrenheit ; N = number of chirps 
per minute. Then 
N — 40 
T=5°+ • 
4. 
This would give 100 chirps for 65 de- 
grees Fahrenheit. 
This formula has been tested in 
Massachusetts by Dr. Robert Edes and 
Mr. Walter Faxon, who find that from 
actual records the temperature is 
about 63 degrees to *100 chirps, with an 
error of variation of one degree or less 
in four-fifths of the cases. — The Insect 
Book (Howard). 
When Young Wrens Leave the Nest. 
BY A. ASHMUX KELLY, DOWXINGTOWN, PA. 
It is a common belief that young 
wrens when about to leave the nest for 
the last time do so at night, but this 
was not true of four that we observed. 
The young birds left the nest early one 
forenoon and played around the bushes 
in the yard for several hours. After a 
while they disappeared, but returned 
in a short time, followed subsequently 
by another flight, after which they flew 
about in the open fields, flying well 
and gaining confidence in their powers. 
Best of all, they stayed well above the 
earth, out of the way of lurking cats. 
The parent birds appeared in the yard 
July 1, found a box and occupied one 
week in getting the nest built, after 
which came the eggs, then the hatch- 
ing, with both birds attending strictly 
to business. 
