OBSERVATIONS ON THE NUMBER OF YOUNG OF THE 

 LASIURINE BATS. 



By Marcus Ward Lyon, Jr., 



Aid, Division of Mammals. 



There i.s a very general belief that the number of young produced 

 at a birth l>y bats is usually one, or at most two, so that a recent 

 writer" saj's: " Such an occurrence as four young- in a bat is, I believe, 

 unheard of;"' and rather doubts the correctness of the observations 

 of an experienced collector who recorded an adult female of Lasiunis 

 Ixn'ealis salinse with that number of young. 



While the rule for most bats is one or sometimes two offspring at 

 parturition, yet a careful examination of material and the literature 

 shows the number of young produced at a time by members of the 

 genus Laslvnis and probably Dasypterus is usually double that num- 

 ber. This might safeh' be inferred from the fact that four mammae 

 are found in bats of this group, as has been noted b}- several 

 writers.* In all other bats, so far as the writer is aware, there are two 

 mamm«, each of which is placed near the middle of the outer border 

 of the pectoral muscle. In the Lasiurine bats, in addition to these two, 

 there is a second pair, located more posteriorly, each mamma of which 

 is nearer the back and pretty well up under the wing. (See lig. 3, 

 Plate XVII.) 



As to the number of voung in Las/m'us^ Professor Wilder found 

 three embrvos in each of two specimens of Z. horealls from Massa- 

 chusetts. Dr. Harrison Allen ^ refers to two embryos of L. horealis 

 as twins. An examination of the material in the U. S. National 

 Museum gives the following results: A pregnant female of Lassiunis 

 hlosseviUei from Paraguay (No. 105631) shows on dissection three well- 

 developed fetuses, each with its own membranes and placenta. There 

 are also in alcohol three embryos from the same locality (Nos. 

 105636-8), which the collector, Mr. AV. T. Foster, says were taken 



«01dfield Thomas, Ann. Mag. Nat. Hist., 7th ser., IX, April, 1902, p. 238. 



''Wilder, Popular Science Monthly, YII, 1875, p. 652. Merriam, Mammals of the 

 Adirondacks, Trans. Linn. Soc, Xew York, II, 1886, p. 81. Miller, North American 

 Fauna, No. 13, October 16, 1897, pp. 105, 115. 



^Contrib. Zool. Lab. Univ. Penn., I, 1895, No. 2, p. 22. 



Proceedings U. S. National Museum, Vol. XXVI— 1314. 



425 



