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PSn HE. 



1 J;liiu;try — Miirch 1SS5. 



Metamorimiosks of akctic insects. In 

 the chapter entitled, "Das insektenleben in 

 arktischen landern," which Dr. Christopher 

 Aurivillius contributes to theaccount of A. E. 

 Nordenskidld's arctic investigations, pub- 

 lished this year in Leipzig,* the author says: 

 "Tlie question of the mode of life of insects 

 and of its relation to their environment in 

 the extreme nortli is one of especial interest. 

 Knowing, as we do, that any insect in the 

 extreme north has at the most not more lliaii 

 from four to six weeks in each year for its 

 development, we wonder how certain species 

 can pass through their whole 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 sum- 

 mers. The correctness of this supposition 

 has been completely shown by the interest- 

 ing observations which (J. Sandberg has 

 made upon species of lepidoptera in South 

 Varanger, at 69° 40' north latitude. Sand- 

 berg succeeded in following the de>-elop- 

 ment from the egg onward of some species 

 of the extreme north. Oettcis bore, Schn., 

 a purely arctic butterfly, may be taken r,.s an 

 example. This species never has 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 fol- 

 lowing spring. The pupa, which in closely- 

 related forms, in regions further to the south, 



* NouDENSKIoLD, A. E. Studieii und forscliuiigen 

 vcranhisst durch meine reiscn iin hohcn nordun. An- 

 torisirtc ausgabe. Leipzig, Brockhaus, 1SS5. 9 -j- 521 

 p., S pi,, maps, O. il. 



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 advanta- 

 geous habit in so raw a climate. The imago 

 leaves the pupa after from five to 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 suffi- 

 cient for the development of many butterflies, 

 but that they make use of two or more sum- 

 mers 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 larvae 

 which develop into 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 Sz" 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 was not surely 

 proved that humble-bees occur at so high 

 latitudes, one would not. with a knowletlgc 

 of their mode of life, be inclined to believi- 

 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 conopidae among the 

 flies, the mutillas among the hymcnoptera. 

 and others." 



Nos. 126-12S wt-rc issued irt March 1SS5. 



