360 ANNUAL OF SCIENTIFIC DISCOA r ERY. 



their larvae and eggs, and a few cherries; of worms and cherries they can 

 procure but few, and those during but a short period, and they are obliged 

 therefore to subsist principally upon the great destroyers of leaves, canker- 

 worms, and some other kinds of caterpillars and bugs. If each robin, old 

 and young, requires for its support an amonnt of these equal to the weight 

 consumed by his bird, it is easy to see what a prodigious havoc a few hun- 

 dreds of them must make upon the insects of an orchard or a park. Is it 

 not, then, to our advantage, he asks, to purchase the service of the robins at 

 the price of a few cherries ? There has lately been some improvement in 

 preserving our birds, and with a little more protection, he thinks that such 

 an increase of them might be obtained as would save us from all the labor 

 required for the appliances of tar, oil, zinc plates, and all other methods by 

 which we seek, with very imperfect success, to destroy our mischievous 

 insects. 



Dr. C. T. Jackson observed, that it was the opinion of Mr. Townend 

 Glover, now engaged by the U. S. Patent Office in studying the insects inju- 

 rious to cotton and other American crops, that among the most inveterate 

 foes to noxious insects are insectivorous insects themselves. 



ON THE CHANGE OF COLOR IN BIRDS AND ANIMALS. 



At a late meeting of the Boston Society of Natural History, Dr. D. F. 

 Wcinland called attention to a question now discussed in the European 

 journals of Ornithology, viz., The cause of the change of color in the 

 feathers of birds, and in the hairs of mammalia, and the manner in which 

 this change is effected. 



It is a well-known fact that many birds, particularly the males, have a 

 very differently colored plumage in different seasons; for instance, that the 

 male of many singing birds has a far more beautiful plumage in the repro- 

 ductive season than during the rest of the year: furthermore, that many 

 northern birds and mammalia become pure white in winter, while they are 

 yellow, red, brown, gray, or of a still darker color in summer. 



Till within the last few years, this change of color was supposed to be 

 effected simply by the production of a new feather or hair; but there are on 

 record several instances which are entirely at variance with this supposition; 

 and Dr. Weinland was of the opinion, that, although this change is gener- 

 ally produced by molting, many instances are proved, by past and recent 

 observations, in which it has taken place without loss of the feather. 



Human Pathology has shown many cases, in which the hair of men, from 

 sudden terror or from grief, has turned gray or white in so short a time (some- 

 times in one night) that there was no possibility of a change of the hair 

 itself. A case is known in Ornithology, in which a starling in one day 

 became white all over, after being rescued from the claws of a cat. 



These facts, however, seemed to be exceptions only, till quite recently 

 some distinguished ornithologists Schlegel in Leyden, and Martin in Ber- 

 lin at the same time affirmed that many birds get their wedding plumage with- 

 out molting. 



Experiments were made by many ornithologists ; some affirmed the new 

 statement, others denied it. But the most striking observation which had 

 come to the knowledge of Dr. Weinland, was made by a friend of his, Mr. 

 Junghaus, of Berlin, on a blue-throated warbler (Sylvia suecica), which he 

 had in a cage. From June, 18-34, till the middle of February, 1855, the 



