In the chapter entitled "Das insektenleben in arktischen ländern," which
Dr. Christopher Aurivillius contributes to the account of A.E.
Nordenskiöld's Arctic investigations, published this year in Leipzig,[2]
the author says: "The question of the mode of life of insects and of its
relation to their environment in the extreme north is one of especial
interest. Knowing, as we do, that any insect in the extreme north has at
the most not more than from four to six weeks in each year for its
development, we wonder how certain species can pass through their
metamorphosis in so short a period. R. McLachlan adverts, in his work
upon the insects of Grinnell Land, to the difficulties which the
shortness of the summer appears to put in the way of the development of
the insects, and expresses the belief that the metamorphosis which we are
accustomed here to see passed through in one summer there requires
several summers. The correctness of this supposition has been completely
shown by the interesting observations which G. Sandberg has made upon
species of lepidoptera in South Varanger, at 69° 40' north latitude.
Sandberg succeeded in following the development from the egg onward of
some species of the extreme north. _Oeneis bore_, Schn., a purely Arctic
butterfly, may be taken as an example. This species has never been found
outside of Arctic regions, and even there occurs only in places of purely
Arctic stamp. It flies from the middle of June onward, and lays its eggs
on different species of grass. The eggs hatch the same summer; the larva
hibernates under ground, continues eating and growing the next summer,
and does not even then reach its full development, but winters a second
time and pupates the following spring. The pupa, which in closely related
forms, in regions further to the south, is suspended free in the air upon
a blade of grass or like object, is in this case made in the ground,
which must be a very advantageous habit is so raw a climate. The imago
leaves the pupa after from five or six weeks, an uncommonly long period
for a butterfly. In more southern regions the butterfly pupa rests not
more than fourteen days in summer. The entire development, then, takes
place much more slowly than it does in regions further south. Sandberg
has shown, then, by this and other observations, that the Arctic summer,
even at 70° N., is not sufficient for the development of many
butterflies, but that they make use of two or more summers for it. If
then more than one summer is requisite for the metamorphosis of the
butterflies, it appears to me still more likely that the humble-bees need
more than one summer for their metamorphosis. With us only the developed
female lives over from one year to the next; in spring she builds the new
nest, lays eggs, and rears the larvæ which develop into the workers, who
immediately begin to help in the support of the family; finally, toward
autumn, males and females are developed. It seems scarcely credible that
all this can take place each summer in the same way in Grinnell Land, at
82° N., especially as the access to food must be more limited than it is
with us. The development of the humble-bee colony must surely be quite
different there. If it is not surely proved that the humble-bees occur at
so high latitudes, one would not, with a knowledge of their mode of life,
be inclined to believe that they could live under such conditions. They
seem, however, to have one advantage over their relatives in the south.
In the Arctic regions none of those parasites are found which in other
regions lessen their numbers, such as the _conopidæ_ among the flies, the
mutillas among the hymenoptera, and others."--_Psyche._
[Footnote 2: Nordenskiöld, A.E., Studien und forschungen veranlasst durch
meine reisen im hohen norden. Autorisirte ausgabe. Leipzig, Brockhaus,
1885, 9 + 581 pp., 8 pl., maps, O. il.]
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