July 21, 1906.] 
FOREST AND STREAM. 
93 
Some Common Insects. 
BY CLARENCE M. WEED. 
II. - The Ichneumon Parasites. 
There are numberless ways in which nature 
keeps that balance of life which renders human 
existence upon the earth possible. One of the 
most interesting of these is fro be found in the 
simple method by which the undue increase of 
plant-feeding insects is prevented through the 
action of the parasite called ichneumon flies. 
A large proportion of these ichneumon flies 
live, in their earlier stages, within'or upon the 
bodies of plant-feeding caterpillars, developing 
at the expense of the lives of the latter. Were 
it not for these parasites there is no question 
that the caterpillars which live upon the foliage 
of trees and other plants would be vastly more 
numerous than they are now and would cause 
untold damage to forests and cultivated crops. 
The life history of one of these ichneumon 
flies may perhaps be made clear with the help 
of the accompanying picture of a butterfly 
chrysalis shell and the ichneumon fly that 
emerged from it. Some weeks before this fly 
emerged, another fly similar to the one pictured 
deposited an egg in or upon the body of the 
caterpillar which was to change to this chrysalis, 
or possibly in the chrysalis itself. This egg 
shortly hatched into a minute grub-like larva, 
which, hidden beneath the skin of the host in¬ 
sect, absorbed its body juices and gradually in¬ 
creased in size. This parasitic grub was of a 
whitish color with the simplest sort of an organ¬ 
ization, living the lazy life of a parasite. As it 
grew larger it absorbed more and more of the 
vitals of its host, until at last nothing was left 
but the outer skin of the chrysalis. 
This chrysalis skin now serves as a protection to 
the parasitic larva, and within it the latter it¬ 
self changes to the pupa or chrysalis state. It 
remains in this pupal condition for a week or 
more, when it again changes to an adult fly, 
similar in appearance to the one that laid the 
egg in the first place. It then gnaws a hole 
through the skin of the outer chrysalis, through 
which it emerges to fly about in the air, visiting 
flowers in search of nectar and hunting through 
the fields and woods for caterpillar victims in 
order that it‘ may deposit eggs in them and 
thus continue the cycle of insect existence. 
In the case of this ichneumon fly the parasite" 
is a comparatively large insect, approximating 
in size that of the host insect on which it de- 
SPHINX CATERPILLAR WITH COCOONS OF PARASITE. 
Photo by A. PI. Verrill. 
velops, and in such cases only a single parasite 
develops in each host. There are many ichneu¬ 
mon flies, however, which are exceedingly 
minute, and when, as is often the case, these 
attack good-sized caterpillars, a large number 
of the parasites commonly develop within the 
body of the host caterpillar. One may very 
often find in the summer time the large cater¬ 
pillars of the Sphinx moth family, which have 
upon their bodies great numbers of small silken 
cocoons, which, to the uninitiated, often seem to 
be insect eggs. A caterpillar carrying this 
curious load is shown in an accompanying 
picture from a photograph by Mr. A. Id. 
Verrill. 
These are by no means the eggs of the cater- 
ICHNEUMON FLY AND BUTTERFLY CHRYSALIS. 
Photo by A. H. Verrill. 
pillar that carries them. Instead, they are the 
cocoons of the ichneumon parasites, and their 
presence is a pretty certain indication that the 
unfortunate caterpillar which carries them will 
die before becoming a winged moth. The story 
of their origin is essentially similar to that of 
the ichneumon fly already given. Several weeks 
before the caterpillar was photographed there 
had lit upon its back a very small ichneumon 
fly which had deposited through the skin of the 
caterpillar a great many tiny eggs. These eggs 
soon hatched into little maggot-like larvae which 
absorbed the life juices of the caterpillar, and 
as the weeks went by gradually increased in 
size. At last they were full-grown in this larval 
state, and in a most curious way they all bur¬ 
rowed through the outer skin of the caterpillar 
at the same time, and each small larva spun 
around itself a silken cocoon, these cocoons, in 
the case of the species illustrated, being held so 
closely together that they formed a single mass. 
In other species the cocoons are not so closely 
attached to one another. 
After the small larvae had thus spun cocoons 
around themselves, each changed into a minute 
chrysalis, from which, in due time, there would 
come a small fly like the one that, weeks be¬ 
fore, lit upon the back of the caterpillar; and the 
Sphinx caterpillar itself will linger along in an 
apparently half-paralyzed condition until it finally 
dies. 
These examples are typical illustrations of the 
life histories of the ichneumon flies, although 
these life histories are marvelously varied in 
their details. Very commonly there are para¬ 
sites upon the parasites, the parasites of 
the caterpillar being called primary para¬ 
sites, and the parasites of the parasites 
being called secondary parasites. Nor does 
this hyper-parasitism necessarily stop here, for 
there are tertiary and even quarternary para¬ 
sites; so that in the light of our modern knowl¬ 
edge we realize that Dean Swift was no mean 
enromologist when he wrote, so many years 
ago, those familiar lines: 
So, naturalists observe, a flea 
Has smaller fleas that on him prey; 
And these have smaller still to bite ’em; 
And so proceed ad infinitum. 
The Forest and Stream may be obtained from 
any newsdealer on order. Ask your dealer to 
supply yon regularly. 
Ruffed Grouse. 
Editor Forest and Stream: 
I have just finished reading Prof. C. F. Hodge’s 
very interesting account of rearing grouse. It 
is published in the report of the Massachusetts 
Commissioners on Fisheries and Game, Pub. 
Document, No. 25. 
I have two special reasons for my interest in 
the article. First, because of my long careful 
study of the birds in a wild state, and second, 
because I have contemplated for several years an 
attempt to rear grouse in captivity. Unfortu¬ 
nately, my financial affairs have prevented the 
necessary expense from being set aside to make 
the experiment. I have some idea of how a 
wired-in inclosure could be made to simulate, in 
some degree, the wild state. 
Prof. Hodge’s deductions on the mating of the 
ruffed grouse led me to write this article. Prof. 
Hodge will agree with me when I state that the 
actions of a bird in captivity cannot afford a 
sure standard by which to judge a bird in the 
wild state. The attempt of his male grouse to 
kill its mate led him to make the following state¬ 
ment : 
‘"The above would indicate that the mating 
occurs but once in a season, that the cocks drive 
the hens away after mating, and that probably 
the drumming is for the purpose of attracting 
unmated hens.” 
Of course Prof. Hodge puts this idea out as a 
suggestion, and not as a fact. If he had had my 
opportunity to study the grouse in a wild state, 
I think he would find his deduction unwarranted. 
So far as I have been able to discover, during 
twenty-one years of careful observation, there is 
a drummer for every sitting • hen. Two birds 
visit my cabin dooryard for food, and I know that 
they have been mated for four seasons. I will 
give my record the present season, of this pair, 
up to date, June 18. 
April 15, (Sunday) at nine o’clock, I heard the 
male drumming near the cabin. I found him on 
a boulder about two hundred feet from the door- 
yard. From past experience, I knew the hen was 
nea'r by, and on the nest. The next day I found 
the nest near a small boulder and not twenty 
feet from a woodland path. It contained one 
egg. That day, April 16, the grouse drummed 
during the noon hour. Later I found the second 
egg in the nest. April 17. the grouse begun to 
drum at 3 o’clock. The hen was on the nest and 
I watched her twenty-two minutes, the male 
drumming meanwhile. When the hen left the 
nest, she was joined by the male, and together 
they wandered down a valley, stopping now and 
then to dig with their bills in the soft soil. The 
next day, April 18, the hen did not lay and the 
male did not drum. April 19, I heard the drum¬ 
ming at 5 o'clock. I visited the nest before go¬ 
ing to the city, and found that it contained four 
eggs. When I returned, several crows flew away 
from the nesting site. Investigation proved that 
the black scamps had located the nest. 
April 20, at 9 o’clock in the morning, I heard 
drumming near the cabin. The hen had selected 
a nesting site near by, and the male had taken 
his stand on a boulder about one hundred feet 
from the cabin dooryard. Two eggs were laid 
in the nest and afforded a dinner for a black 
snake. I killed the snake, but the birds left the 
locality. The next attempt was made on a rocky 
hillside, too far away for a daily record, so I visited 
the nest from time to time. May 6 it contained 
eleven eggs and the hen began to sit. Finding the 
drumming had ceased May 12, I was led to visit 
the nest, and as I expected, found it looted. This 
time by crows, doubtless, as they nested in a pine 
grove near the spot. 
I did not hear drumming until May 17. I found 
the nest and hung a white flag on a bush near by, 
hoping to keep the crows away. The scamps 
seemed to respect a flag of truce, so the grouse 
brought off eight chicks. I came onto the batch 
yesterday. June 18, and there were six only. As 
these six are stocky and good flyers, they may 
pull through. 
The question might arise as to how I know that 
the nests described belong to one pair of grouse; 
or, how can I be sure of my birds from year to 
year? I know them because they are the only 
grouse that visit my cabin dooryard. And too, 
