June, 1919 
FOREST AND S T R E A !M 
285 
kind of egg is the oval type, but to this 
shape there are many exceptions. The 
eggs of snipes and plover are distinctly 
conical, and, lying in the nest with their 
points inward, can be easily covered by 
the small-bodied parent. Auks and 
murres lay their eggs on narrow ledges 
or shelvings of steep cliffs, and, remarka- 
bly enough, the eggs of these birds are 
long and pyriform, and often attenuate 
in a sensibly concave curve toward the 
smaller end. Hence, when moved sud- 
denly as the brooding bird leaves the 
ledge, the egg describes a circle about 
its apex instead of rolling into the sea. 
Birds which for the most part build their 
nests in holes in trees or similar places, 
produce eggs that are nearly spherical. 
Such birds are the owls and woodpeck- 
ers, whose eggs cannot possibly fall out 
of the nest, and which, owing to their 
rounded outline, occupy little space in 
the bowl-shaped cavity. 
As might be expected, size in eggs de- 
pends primarily upon the size of the 
bird. It also depends somewhat upon 
the number of eggs in the normal clutch ; 
the eggs of a bob-white, which may num- 
ber as many as sixteen, or even more, are 
smaller than those of the less pi-olific 
woodcock. But the principle indicator 
of size is the condition of the young birds 
when first hatched. Precocial birds, or 
species in which the young are ready to 
leave the nest at birth are hatchec from 
relatively larger eggs than altricial or 
nest-reared species. Thus the eggs of 
the robin and song sparrow are propor- 
tionately smaller than those of the 
spotted sandpiper. The young robins 
and sparrows, which are hatched naked 
and helpless, are reared in a well con- 
structed nest. Young sandpipers on the 
contrary, never know a nest other than 
a slight depression in the ground, and 
when hatched they are covered with down 
and ready to run about immediately. 
W ITH regard to the coloration of 
eggs, a multiplicity of exceptions 
prevents the framing of universal 
laws. Certain facts, however, do hold 
fairly constant. The eggs of nearly all 
birds that lay in holes are white, and 
it should be noted that in such cases 
markings would be of no protective value. 
Owls, woodpeckers, and swifts all demon- 
strate this rule. The eggs of birds which 
lay on the ground are often so marked 
that they are inconspicuous. The eggs 
of the whip-poor-will blend into indis- 
tinctness among the fallen leaves and 
this principle is still more strikingly il- 
lustrated by the eggs of snipes, gulls and 
terns, for so closely do these resemble the 
pebbles among which they are laid that 
it is very difficult to distinguish them. 
The nest of a precocial bird 
Individual variation in the color of 
eggs is astonishingly great, and may be 
due to a number of physiological reasons. 
A bird in the prime of health and ma- 
turity usually lays eggs that are more 
profusely marked than those of a young 
or very old bird. The pigment is nor- 
mally deposited more heavily upon the 
large end of the egg, and this has been 
shown by actual observation to be the 
end which passes first down the oviduct. 
Occasionally, through accident, the posi- 
tion may become reversed, and the heav- 
ier deposition made upon the smaller 
end. This phenomenon occurs with par- 
ticular frequency among the hawks. 
Many kinds of birds illustrate extreme 
individual variation in the color and 
shape of their eggs. Among most species 
of tube-nosed sea-birds, including the 
petrels and albatrosses, the form of the 
single eggs are so variable that it is im- 
possible to describe their specific char- 
acters beyond stating that they are white, 
and giving their approximate dimen- 
sional limits. Eggs of crows and jays^ 
among the higher birds, are apt to bfr 
very variable in color. Mr. W. L. Daw- 
son, Director of the Museum of Com- 
parative Oology, found that a large ser- 
ies of eggs of a certain jay which in- 
habits one of the islands off the Cali- 
fornia coast exhibited remarkably little 
variation, whereas those of its most 
closely related neighbor on the mainland 
were extraordinarily variable. He there- 
fore came to the interesting conclusion 
that the island sub-species of jay had 
descended from not more than a single 
pair of the mainland birds, and that the 
unusual similarity of all the island eggs 
was due to a genuine “family likeness.” 
Chance, therefore, plays but an unimpor- 
tant part in the wide diversity of eggs, 
and all their characteristics are but 
different phases of the expression of uni- 
versal, determinate, biological laws. 
PLANT LICE AND SCALE INSECTS 
NOTES ON THE NATURAL HISTORY OF THE TINY DEPREDATORS OF GARDEN AND OR- 
CHARD WHICH HAVE HELD THE ATTENTION OF ENTOMOLOGISTS FOR SO MANY YEARS 
P LANT lice are found every year on 
almost any kind of plant, but last 
year they were unusually numerous, 
and accordingly did more or less serious 
injury. Potatoes, of all the crops, seemed 
to suffer more severely than any other 
plant. Numerous lice infested the under- 
side of the leaves and tender stalks of 
the potato vines, from which they sucked 
the juices. The amount of sap extracted 
by the lice was more than the plants 
could stand, and in a short time the vines 
dried up before the tubers were full 
grown, which lessened the value of the 
crop considerably. 
Plant lice are sucking insects; they do 
not chew the leaves, as potato bugs or 
caterpillars do, but feed only on the 
liquid which they draw from a puncture. 
No matter how much poison may have 
been put on the leaves, it will scarcely 
affect them, for any poison, whether 
liquid or powder, would have to come into 
direct contact with each individual. 
By R. C. M. 
The worst enemy of plant lice is a 
minute parasitic wasp. Last summer- 
numerous dead plant lice, parasitized by 
this wasp could be seen on the leaves 
and stems of vegetables throughout the 
northeastern states. Their bodies had 
become inflated and hardened, and the 
color had changed from green or reddish 
to a yellowish gray. Such dead plant 
lice are often mistaken for insect eggs 
and are destroyed, but they should rather 
be left undisturbed for the larva of the 
useful parasitic wasp feeds inside the 
dead body of the louse. 
Plant lice multiply more rapidly than 
perhaps any other insects. The first 
plant lice, called stem-mothers are wing- 
less, and appear when the leaf buds begin 
to show. They begin feeding and for 
several days give birth to about eight or 
ten young each day. In ten or twelve 
days the young are full grown, and also 
start to reproduce young. This repro- 
duction, when it once begins, is in the 
nature of a continuous performance, and 
by the time the leaves are fully formed, 
the surfaces are covered by plant lice; 
so, instead of unfolding and reaching 
full size, they are curled, crippled and 
often discolored. After the second gen- 
eration of plant lice there will be more 
individuals than a tree or plant can 
maintain; therefore in the third and 
later generations some of the individuals 
are wingless and others have wings. The 
latter fly to other trees and plants on 
which they start new colonies. All the 
plant lice including the stem-mothers are 
sexless, and reproduce young without 
the co-operation of the male. The repro- 
duction continues until the end of the 
season, but the last generation consists 
only of males and females. A union of 
these produces minute eggs from which 
in spring the sexless stem-mothers 
emerge. The habits of the numerous 
kinds of plant lice vary. Some live on 
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