196 THE INDUSTRIES OF ANIMALS. 



tion which cannot well be called anything else but 

 sewing it.^ 



Modifications of dwellings according to season and 

 climate.— K certain number of facts show that these 

 various industries are not fixed and immutable in- 

 stincts imposed on the species. Certain Birds change 

 the form of their dwelling according to the climate, 

 or according to the season in which they inhabit it. 

 For example, the Crossbill, Loxia tcBiiioptera (Fig. 32), 

 does not build its nest according to the same rules 

 in Sweden as in France. It builds in every season. 

 The winter shelter is spherical, constructed with very 

 dry lichens, and it is very large. A very narrow 

 opening, just sufficient for the passage of the owner, 

 prevents the external cold from penetrating within. 

 The summer nests are much smaller, in consequence 

 of a reduction in the thickness of the walls. There is 

 no longer need to fear that the cold will come through 

 them, and the animal gives itself no superfluous 

 trouble. 



Again, the Baltimore Oriole, which inhabits both the 

 Northern and Southern Statesof North America, knows 

 very well how to adapt his manner of work to the 

 external circumstances in which he lives. Thus, in 

 the Southern States the nest is woven of delicate 

 materials united in a rather loose fashion, so that the 

 air can circulate freely and keep the interior fresh ; 

 it is lined with no warm substance, and the entrance 

 is turned to the west so that the sun only sends into 

 it the oblique evening rays. In the north, on the 

 contrary, the nest is oriented to the south to profit by 

 all the warm sunshine ; the walls are thick, without 



' McCook describes, and gives good illustrations of, these nests in 

 various stages of progress, Animcan Spiders, vol. i. p. 302. 



