2 BROOKLYN IXSTITUTU MUSEUM. SCIENCK BULLETIN 2. I. 
male, causes a modification of the mucous membrane lining the neck 
of the uterus, so that the canal becomes plugged with coagulated 
secretion. Fertilization does not then ensue as in other mammals : or. 
the contrary, the mass of spermatozoa is held in the uterine chamber 
throughout the lethargy of winter, and not until active life is resumed 
after several months, do the ova descend.* Among Long Island 
species impregnation probably takes place during April. 
Despite the fact that bats have been observed by men in all ages, 
conspicuously little is known of the life histories of even our most 
abundant and familiar species. This is due to their crepuscular or 
nocturnal habits, and to their secretiveness during the long hours 
and seasons in which they are not seen in flight. Sleepiest of mam- 
mals, not excepting even the drowsy Dormouse of the Old ^^'orla. 
the winged fur bearers, who alone in the highest class of creatures 
have realized the envied accomplishment of birds, spend the greater 
part of their lifetime hanging head downward in slumber, and slum- 
ber often so profound that a brief nap may become the ecjuivalent 
of hibernation, accompanied by a fall of temperature and retarding 
of most bodily functions. 
The five species of bats known to inhabit Long Island belong 
to the family Vespertilionidae. the largest and most widely dis- 
tributed division of the order. Several of the species, or possibly 
all of them, make seasonal migrations of unknown extent. They are 
without except'on strictlv insectivorous. 
ARTIFICL^L KEY TO LONG ISL.\ND B.\TS. 
(For purposes of comparison, a Y^ellow Swallowtail Butterfly has a wing expanse up to 5 inches, a 
Goldfinch of about 9 inches, a Chimney Swift 12>2 and a Kingbird 14>j.) 
a. Large. Expanse of wing 12 to 15 inches. 
6. Interfemoral membrane densely furred above. Color mottled brown. 
tawny and white, white predominating below j. Lasiurtts cinereus. 
b'. Interfemoral membrane naked above. Color uniform, above dark 
brown, below buffy gray j. Vesperlitio fusais. 
a'. Not large. Expanse of wing not over 12 inches. 
c. Medium. Expanse of wing 9 to 12 inches. Fur more or less tipped 
with whitish. 
d. Interfemoral membrane densely furred above. Color tawny or 
grayish 4, Lasiurtts borealis. 
d', Interfemoral membrane furred basally only above. Color blackish . 2. Lasionyrteris noctivagans. 
c' . Small. Expanse of wing 9 inches or less. 
c. Five teeth in the side of the jaw behind canine, a single minute 
one immediately behind canine. Color above often mottled, 
below yellow brown (Extra limital) Pit'Strellu^i sttbftavtts. 
e'. Six teeth in the side of the jaw behind canine, two minute ones 
immediately behind canine. Color above almost always uni- 
form, below dark huffy gray. 
/. Ear and tragus slender, the latter 9 mm. or more in length 
(Extra limital) Myotis sttbttlatus. 
f. Ear and tragus short and broad, the latter 8 mm. or less in 
length /. Myotis litcifugus. 
*Rollinot and Trouessart, Mem. Zool. Soc. France. IX. 1896. p. 214: also see 
Rollinor and Trouessart. Mem. Zool. Soc. France. X, 1897. p. lU. 
