98 
POPULAR SCIENCE NEWS. 
[July, 1S90. 
ber of very small drops, which, when 
absorbed by the blotting-paper, give the 
impression of much larger drops than their 
actual size would warrant. 
A WELL-KNOWN Optical illusion is that 
produced by the common tall, or "stove- 
pipe" hat. Let anyone not familiar with the 
facts in the case, try to estimate the compara- 
tive lengths of the height and width of such 
a hat, and he will invariably make the verti- 
cal distance from one-quarter to one-half 
greater than the horizontal one. But, by 
actual measurement, as shown in the engrav- 
ing, the line A-B is longer than C-D ; so th.it 
the very stylish and well-proportioned hat 
there shown is really not a "tall" one by any 
means, but its height is only an optical illu- 
sion produced by the projecting curved brim 
of the hat, which deceives the eye into a false 
perception of the relation between its differ- 
ent dimensions. In connection with this 
subject, we may also mention the fact that a 
horse's head of average size is just the height 
of an ordinary flour barrel, although most 
persons would require the evidence of an 
actual measurement before being convinced. 
The illustrations to this article are repro- 
duced from La Nature. 
[Original in Popular Science Newa.^ 
BRIEF STUDIES IN BIOLOGY. 
BY PROF. JAMES H. STOLLER. 
IV. 
THE GRASSHOPPER. 
At this time of year, no class of animals is more 
readily available for observational study than the 
insects. To those whose special interest is in 
making collections, the beautiful butterflies and 
moths tempt to pleasant rambles and eager pur- 
suits in the open fields. Others, who wish to gain 
broader information in entomological science, will 
seek to obtain specimens of the various orders 
of insects, and will compare them in respect to 
the structure of their bodily parts, their habits, 
food, etc. Whatever line of study is entered upon, 
none will omit to make observations upon the 
transformation, or metamorphosis, of some com- 
mon insect, in its development from the egg stage 
to its full-grown, winged state. There is no simple 
study in biology which is at once so delightful and 
instructive as this ; and, before passing to an exami- 
nation of the insect chosen for special study in this 
paper, a few words of direction for the practical 
study of insect development may be given. 
Obtain a leaf on whicli have been deposited the 
eggs of some common insect. For instance, on the 
leaves of the young cabbage plants may be found in 
small masses the eggs of the cabbage butterfly. 
They are yellow, oval bodies, with ridges running 
lengthwise, and have been well compared in appear- 
ance to ears of yellow corn. Put the leaf with eggs 
attached in a small tin or wooden box, with a piece 
of window-glass for a cover. The egg soon hatches 
into a small green and white worm — the larva 
of the butterfly. Fresh cabbage leaves should be 
supplied the worm for food, and it will be found to 
have no lack of appetite. It is only required now 
to continue observations, noting the passage of the 
larva into the pupa stage, and the final emergence 
from the cocoon of the perfect insect. 
A single remark, of general biological interest, 
may here be made : These transformations in the 
development of the individual insect are in no wise 
different in their nature from the changes through 
which any animal goes in its individual develop- 
ment. The chick which hatches within the shell 
of the egg passes through a series of developmental 
changes of the same nature. The main difterence 
is this : In the case of the insect there is cessation 
of development at the time the larva issues from the 
egg, and, for a time, growth, instead of development, 
of the embryo (larva) takes place. Then growth 
ceases, — when the pupa stage begins, — and develop- 
ment goes on to completion. In the case of the 
chick, on the other hand, development continues, 
without interruption for growth, from the earliest 
embryonic condition to the time when the young 
bird is fully formed. And the explanation of the 
diflerence in the two processes is evidently this : 
In the small insect egg there is insufllcient nourish- 
ment, or food-matter, for the building up of a new 
individual; hence it liatches into a tiny w6rm, 
which gets food for itself, and, as we have seen, is 
not slow in improving its opportunities; the fact is, 
the worm is storing up material in its gorged body 
to complete its development (in the pupa stage) to 
the perfect insect. But in the case of the hen's egg, 
there is abundant nourishment in the white and 
yolk to afford material for the building up of the 
chick without supply from without. 
In harmony with the plan of study of these 
papers, we take, in the present number, a type-form 
of the fourth great group, or sub-kingdom, of ani- 
mals. This group is the Articulata, and includes 
all animals which agree in having bodies showing 
a segmented, or ringed structure, and in having 
jointed appendages. It includes the insects, the 
Crustacea, the arachnida, and the myriopoda. Four 
animals, typical of these four classes of Articulata, 
in the order named, are ; the grasshopper, the lob- 
ster, the house-spider, and the thousand-legs. 
Taking a specimen of any of the several common 
species of grasshopper, it may first be observed that 
the exterior of the body is hard and crust-like, 
(compare with lobster and spider), and that this 
integument is segmented, or jointed, giving the 
body a ringed structure. These rings are most 
evident in the hinder part of the body, or abdomen, 
where there are nine or ten of them, so jointed that 
this region of the body is easily movable. The 
middle part of the body, called the thorax, can 
readily be seen to consist of three rings. In the 
head a ringed structure is not apparent, but the 
paired mouth-parts, and, perhaps,' the antennse and 
eyes, indicate that the head region represents sev- 
eral rings consolidated. 
The grasshopper, or any other member of the 
sub-kingdom Articulata, should be compared with 
the earthworm (see third paper of this series) in 
respect to the ringed structure of the body. It is 
seen that in the latter animal the rings are all 
separate and easily noticeable; but in the members 
of the higher group some of the rings are consoli- 
dated to form more general parts of the body, as 
(in .the grasshopper) head, thorax, and abdomen. 
It is important to observe, too, that, as a rule, there 
are just as many pairs of appendages as there are 
rings; this is well seen in the thousand-legs. In 
the lobster, also, each ring has a pair of appendages ; 
but in insects some are wanting, the abdomen being 
destitute of them. However, in the larval stage 
of insects there are generally as many pairs of legv 
as there are rings. This is well seen in the cater- 
pillar. 
It is characteristic of all insects that the body is 
divided into three pretty distinct parts, namely : 
head, thorax, and abdomen. It is this leature 
of bodily structure, indeed, that gives to the class 
its name, the word freely translated meaning cut 
tn^o^the insect body being cut into these three 
parts. Any insect may also be readily distinguished 
from animals of other classes, by observing whether 
there are three pairs of legs attached to the middle 
region of the body. In this way the larvie of in- 
sects can also be distinguished from worms. In 
the larva, or worm stage of development, insects 
have quite a number of pairs of legs; but the tfiree 
pairs of true legs are always larger than the others, 
and are near the head-end of the body. 
The thorax also bears on its dorsal side two pairs 
of wings. • If the wings are straightened out, it will 
be seen that the fore ones are narrow and straight- 
edged, and tliat the hinder ones fold lengthwise, in 
the manner of a fan. Now the classification of in- 
sects, in regard to the most general groups, — that 
is, the orders, — is based upon the form and structure 
of the wings. Accordingly, tlie grasshopper be- 
longs to the order Orthoptera — straight-winged. It 
will be noted that the fore wings are thicker than 
the other pair, and it is evident that their chief use 
is to serve as covers for the latter, which act solely 
as organs of flight. 
The abdomen forms rather more than lialf tlie 
length of the body. The rings of which it is made 
consist of a dorsal part, or arc, and a ventral arc; 
and it is this structure tliat admits of the movements 
of respiration — the ventral side of the abdomen (as 
one may see by holding the living grasshopper in 
the hand) alternately raising and lowering. In 
each ring, at the sides, is a pair of breathing-pores, 
or spiracles, which admit air in and out of the 
system of branching tubes that penetrate every part 
of the body and constitute the organs of respiration. 
It is instructive to compare this mode of respira- 
tion — which is common to insects, spiders, and 
myriapods — with that of animals that breathe by 
lungs or gills. It is seen that in the former, air is 
conveyed through the branching hollow tubes to 
the tissues in every part of the body. Thus a 
particle of waste matter is oxidized immediately at 
the place in the body where formed. In animals 
that breathe by lungs or gills, on the other hand, 
waste matter is conveyed, through the circulation 
of the blood, from the place where formed to the 
organs of respiration, where air is contained, and 
where the waste is oxidized. 
The grasshopper is an especially interesting 
insect in regard to its organs of sense. The two 
large compound eyes are very noticeable. Under 
magnification their surface is seen to consist of very 
many polygonal plane surfaces, or facets, set at 
various angles, so that from whatever direction light 
falls, it throws an image upon the retina at the back 
