VESPERUGO NOCTIVAGANS. 93 



killed on the first ev-cnini^ of their appearance averaged 90mm. in 

 length by 261 mm. in stretch, hut weighed only half as much as 

 their parents. The adults av^erage about 104mm. in length b)- 

 302mm. in stretch. When on the wing the young may be dis- 

 tinguished from the old by the weakness and hesitancy of their 

 flight, rather than by the difference in size. The young are much 

 more beautiful than the adults, and they alone possess the perfect 

 silvery tips to the hairs from which the species derives its name. 

 Even before going into winter quarters their soft silvery backs 

 have given place to the grizzly coats that characterize the adults. 



My esteemed friend, Mr. William Brewster, has kindly favored 

 me with the following very interesting account of a colony of bats 

 that he discovered during an ornithological excursion into the ex- 

 tensive coniferous forests of western Maine : — • 



" On June 18, 1880, I was searching for woodpecker's nests 

 among- the stubs that line the shores of Lake Umbaeoe, when I 

 noticed a small ragged-looking hole about two feet above the water 

 in a trunk that stood well out on the flooded meadows. I should 

 hardly have turned aside to examine it had I not fancied that I saw 

 something move at its entrance ; accordingly, paddling to the spot, 

 I struck the tree sharply with the butt of an axe. The blow was 

 followed, not by the appearance of a woodpecker's or nuthatch's 

 head, as I had expected, but by an outbreak of shrill squeaking 

 sounds that seemed to come from every part of the interior. As 



have been born within forty-eight hours. The single one, a male, weighed iioo milligrammes, 

 and measured 43mm. in length by 79mm. in extent ; the cord measured 20mm., and the placenta 

 10x14mm. One of the other females contained twins, both of which were females ; one of them 

 weighed 1380 milligrammes, measuring 41mm. in length by 72mm. in stretch; cord i8mm. ; 

 placenta 9x14mm. The other weighed iioo milligrammes, and measured 39x68mm.; cord I7nim. ; 

 placenta 8x13mm. That the young are brought forth in the southern part of the State at about the 

 same date as with us is evidenced from the following. Dr. A. K. Fisher states that a female which 

 he killed at Sing Sing, in Westchester County, June 24, 1881, "contained two young, well de- 

 veloped, and probably would have been delivered in a few days. The young each weighed 1,45c 

 milligrammes. On removing the amnion the ears of one of the young bats became erect. The 

 placenta of this species is different from that of the Little Brown Bat ; instead of being circular it 

 is elliptical, measuring 10 by 15 millimetres. The placentae were attached to the posterior wall of 

 the uterus near the summit of each cornu. The umbilical cord measured twenty millimetres in 

 length." (Forest and Stream, Vol. XVI, No. 25, July 21, 1881. p. 490.) 



