Chapter 2

Published December 29, 1961

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY JEAN M. NEIBARGER, STATE PRINTER TOPEKA, KANSAS 1961

North American Yellow Bats, "Dasypterus," And a List of the Named Kinds Of the Genus Lasiurus Gray

BY

E. RAYMOND HALL AND J. KNOX JONES, JR.

INTRODUCTION

Yellow bats occur only in the New World and by most recent authors have been referred to the genus _Dasypterus_ Peters. The red bats and the hoary bat, all belonging to the genus _Lasiurus_ Gray, also occur only in the New World except that the hoary bat has an endemic subspecies in the Hawaiian Islands.

The kind of yellow bat first to be given a distinctive name was the smaller of the two species that occur in North America. It was named _Nycticejus ega_ in 1856 (p. 73) by Gervais on the basis of material from the state of Amazonas, Brazil, South America, but was early recognized as occurring also in North America (in the sense that México and Central America, including Panamá, are parts of North America). More than 40 years elapsed before subspecific names were proposed for the North American populations; Thomas named _Dasypterus ega xanthinus_ in 1897 (p. 544) from Baja California, and _Dasypterus ega panamensis_ in 1901 (p. 246) from Panamá.

The larger of the two North American species was named _Lasiurus intermedius_ in 1862 (p. 246) by H. Allen on the basis of material from extreme northeastern México. Another alleged species, _Dasypterus floridanus_, was named in 1902 (p. 392) by Miller from Florida, but as set forth below it is only a subspecies of _L. intermedius_, a species that is seemingly limited to parts of the North American mainland and Cuba.

A third species, _Atalapha egregia_, allegedly allied to the small yellow bat, _L. ega_, was named in 1871 (p. 912) by Peters from Santa Catarina, Brazil, but Handley (1960:473) thinks that _L. egregius_ is allied instead to the red bats. The species _L. egregius_ has not been studied in connection with the observations reported below.

Bats of the genus concerned were given the generic name _Nycteris_ by Borkhausen in 1797 (p. 66), and the name _Lasiurus_ by Gray in 1831 (p. 38). For much of the latter part of the 19th century the generic name _Atalapha_ proposed by Rafinesque in 1814 (p. 12) was used because it antedated the name _Lasiurus_. In this period Harrison Allen (1894:137) raised to generic rank the name _Dasypterus_ that had been proposed by Peters in 1871 (p. 912) only as a subgenus for the yellow bats. Since 1894 the yellow bats ordinarily have borne the generic name _Dasypterus_. The red bats and the hoary bat continued to be referred to as of the genus _Atalapha_ until early in the 20th century when it was decided that a European bat of another genus was technically the basis for the name _Atalapha_. Thereupon _Lasiurus_ was again used in the belief that it was the earliest available name for the bats concerned. But in 1909 (p. 90) Miller showed that the name _Lasiurus_ was preoccupied by _Nycteris_ Borkhausen, 1797 (p. 66). From 1909 until 1914 in conformance with the Law of Priority _Nycteris_ was used for the red bat and the hoary bat.

At this point it is desirable to digress and indicate why and how the Law of Priority came into being. In the 19th century different technical names were used for the same kind of animal depending on the opinions of individual authors. For example, one author used name A because it was most descriptive of the morphology of the animal, another author used name B because it had been used more often than any other, another author used name C because it was more euphonious, etc. In order to achieve uniformity and stability a set of rules was drawn up in 1901 at the International Zoological Congress in Berlin. Those rules were based principally on the rule, or law, of priority. In effect, the law stated that the technical name first given to a kind of animal (with starting date as of January 1, 1758, _Systema Naturae_ of Linnaeus) would be the correct and official name. After the mentioned rules were adopted, some zoologists, mostly non-taxonomists, objected to the rules and in response to these objections a compromise was adopted in 1913 at the International Zoological Congress in Monaco and the International Committee on Zoological Nomenclature was authorized to set aside, at its discretion, the Law of Priority. In 1913 it was thought by everyone that the names conserved (_nomina conservanda_) by setting aside the rules would be few.

Returning now to the generic names applied to the bats concerned, it is to be noted that from 1803 until 1909 _Nycteris_ had been used as the generic name of an African bat on the erroneous assumption that the name was first applied in a valid fashion to the African bat. With the aim of conserving the name _Nycteris_ for the African bat, some zoologists petitioned the International Committee on Zoological Nomenclature to set aside the Law of Priority and petitioned also that the name _Lasiurus_ be validated for use again as the generic name for New World bats. This petition was granted in 1914 in the first lot of names for which exception to the rules was made. As a result, since 1914 _Lasiurus_ has been used with increasing frequency, and _Nycteris_ with decreasing frequency, for New World bats.

The above explanation of the application of the generic names _Nycteris_, _Atalapha_, and _Lasiurus_ is given for two reasons: First, study of more abundant material than was available to Harrison Allen in 1894 when he raised _Dasypterus_ to generic rank reveals, as set forth beyond, that the yellow bats are not generically different from the red bats and hoary bat and so will bear the same generic name that is applied to the red bat and hoary bat; second, a choice of generic names has to be made. Actually, the International Commission on Zoological Nomenclature since 1913 has voted to make many, instead of only a few, exceptions to the rules. The number of names resulting from these exceptions is becoming so large that some zoologists fear that the chaotic condition of nomenclature in the previous century will return. Those who hold such fears maintain that adherence to the rules of 1901, or to the Law of Priority, or at least to some rules, clearly is desirable. Certainly there is much logic in that view. According to the rules, _Nycteris_ is the correct name of the bats concerned. According to the Commission, it is well to use instead the name _Lasiurus_. Perhaps the time has come to follow the rules and use _Nycteris_. But, because of the possibility that the Commission will return to its policy of 1913 and recommend only a few instead of many exceptions to the rules, the generic name _Lasiurus_ is tentatively used in the following accounts.

Genus Lasiurus Gray

Hairy-tailed Bats

1797. _Nycteris_ B[orkhause]n, Der Zoologe (Compendiose Bibliothek gemeinnützigsten Kenntnisse für alle Stände, pt. 21), Heft 4-7, p. 66. Type, _Vespertilio borealis_ Müller [= _Lasiurus borealis_]. _Nycteris_ Borkhausen is a homonym of _Nycteris_ G. Cuvier and É. Geoffroy St.-Hilaire, 1795, type _Vespertilio hispidus_ Schreber, 1774 [= _Nycteris hispida_], from Senegal. Although _Nycteris_ Cuvier and Geoffroy St.-Hilaire is a _nomen nudum_, Opinion 111 of the International Commission of Zoological Nomenclature establishes the name as available for a genus of Old World bats. On this basis, _Nycteris_ Borkhausen is not available for the New World genus. _Nycteris_ É. Geoffroy St.-Hilaire, 1803, is a synonym of _Nycteris_ Cuvier and Geoffroy St.-Hilaire, 1795, as given status by the Commission.

1831. _Lasiurus_ Gray, Zool. Misc., No. 1, p. 38. Type, _Vespertilio borealis_ Müller.

1871. _Atalapha_ Peters, Monatsber. K. Preuss. Akad. Wiss., Berlin, p. 907, and other authors [_nec Atalapha_ Rafinesque, 1814].

_Type species._--_Vespertilio borealis_ Müller.

_Diagnosis._--Interfemoral membrane large and most of its upper surface furred; mammae 4; third, fourth and fifth fingers progressively shortened; ear short and rounded; skull short and broad; nares and palatal emargination wide and shallow (width transversely exceeding length anteroposteriorly); sternum prominently keeled; i. 1/3, c. 1/1, p. 1/2 or 2/2, m. 3/3; when two upper premolars present, anterior one minute, peglike, and displaced lingually; M3 much reduced, area of its crown less than a third that of M1.

Members of this genus are notable for having three and even four young (more than other bats). In North America at least _L. borealis_ and _L. cinereus_, are migratory.

Provisional Key to the Recent Species of _Lasiurus_

1. Color reddish or grayish (not yellowish); normally two premolars on each side of upper jaw.

2. Occurring on Antillean islands (color reddish).

3. Length of upper tooth-row less than 4.5 mm. (occurring on Hispaniola and Bahamas) _L. minor_.

3'. Length of upper tooth-row more than 4.5 mm. (not occurring on Hispaniola and Bahamas).

4. Greatest length of skull less than 13.9 mm. (occurring on Cuba) _L. pfeifferi._

4'. Greatest length of skull more than 13.9 mm. (occurring on Jamaica) _L. degelidus._

2'. Occurring on mainland and coastal islands of North and South America; also on Galapagos and Hawaiian islands (color reddish or grayish).

5. Total length more than 120 mm.; color grayish _L. cinereus._

5'. Total length less than 120 mm.; color reddish.

6. Upper parts brick red to rusty red, frequently washed with white; lacrimal ridge present.

7. Not occurring on Galapagos Islands _L. borealis._

7'. Known only from Galapagos Islands (both ear of 7.6 mm. and thumb of 6.4 mm. allegedly shorter than in _L. borealis_ of adjacent mainland; presence of lacrimal ridge not verified) _L. brachyotis._

6'. Upper parts not brick red to rusty red; lacrimal ridge not developed.

8. Forearm more than 46.5 mm. (48 in only known specimen, a male); dorsum bright rufous (absence of lacrimal ridge not verified) _L. egregius._

8'. Forearm less than 46.5 mm.; dorsum not bright rufous.

9. Upper parts mahogany brown washed with white; forearm less than 43 mm _L. seminolus._

9'. Upper parts deep chestnut; forearm more than 43 mm. (44.8 in only known specimen, a female) _L. castaneus._

1'. Color yellowish; only one premolar on each side of upper jaw.

10. Total length more than 119 mm.; length of upper tooth-row 6.0 mm. or more _L. intermedius._

10'. Total length less than 119 mm.; length of upper tooth-row less than 6.0 mm _L. ega._

Lasiurus intermedius

Northern Yellow Bat

_Diagnosis._--Upper parts yellowish-orange, or yellowish brown, or brownish-gray faintly washed with black to pale yellowish gray; size large (forearm, 45.2-62.8; condylocanine length, 16.9-21.5).

_Distribution and Geographic Variation_

_Lasiurus intermedius_ H. Allen, type from Matamoros, Tamaulipas, has been reported from the Rio Grande Valley of Texas southward to Honduras and in Cuba. _Lasiurus floridanus_ (Miller), type from Lake Kissimmee, Florida, has been recorded from southeastern Texas, eastward along the Gulf of Mexico to Florida, and thence northward along the Atlantic Coast to extreme southeastern Virginia (see records of occurrence beyond and Fig. 2). Specimens of _intermedius_ from the vicinity of the type locality and from other localities in México differ from specimens of _floridanus_ (from Florida and southern Georgia) as follows: Larger, both externally (especially forearm) and cranially (see measurements); teeth larger and heavier; skull heavier and having more prominent sagittal and lambdoidal crests; braincase less rounded, more elongate; auditory bullae relatively smaller; upper parts averaging brighter (yellowish to yellowish-orange in general aspect, rather than yellowish-brown to brownish-gray).

The differences mentioned above are of the magnitude of those that ordinarily separate subspecies of a single species rather than two species. Miller (1902:392-393), in the original description of _floridanus_, noted that the differences between it and _intermedius_ were slight and remarked (p. 393): "Indeed, it is probable that it intergrades with the Texas animal." Lowery (1936:17) also has suggested that intergradation might occur between _intermedius_ and _floridanus_ "in southwestern Louisiana or eastern Texas"; later (1943:223-224) he pointed out that specimens from Baton Rouge, Louisiana, averaged larger in cranial dimensions than typical _floridanus_ and again mentioned the possibility of intergradation between the two kinds. Sanborn (1954:25-26) touched obliquely on the problem when he wrote: "In Florida, _Dasypterus intermedius_ is referred to as a Florida yellow bat (_Dasypterus floridanus_)." Handley (1960:478) wrote that certain morphological similarities suggested "gene flow" between the two kinds.

Specimens examined from Louisiana resemble _floridanus_ from Georgia and Florida to the eastward in external dimensions. Some of those specimens resemble _floridanus_ in size of skull, but two skulls from Louisiana are inseparable from those of topotypes of _intermedius_. The upper parts of specimens from Louisiana are generally like those of animals to the east but average somewhat paler (less brownish). The specimens seen from Louisiana seem to be intergrades between _intermedius_ and _floridanus_ but clearly are assignable to the latter.

The picture is less clear as regards bats from southeastern Texas (one specimen each from Colorado and Travis counties, and four specimens from Harris County). Five of the specimens have skulls (the Travis County specimen is a skin only) and of these, four are clearly assignable, on the basis of size and shape of the skull, to _intermedius_. The fifth skull (specimen from Colorado County) is intermediate in size between _floridanus_ and _intermedius_ and on that basis alone could be assigned with equal propriety to either. All these specimens from Texas more closely resemble _floridanus_ than _intermedius_ in external size (forearms: 49.2, 49.6, 50.7, 49.9 (approximate), 49.6, 49.1). The pale yellowish-gray upper parts of the four adults, seemingly resulting from a dilution of the brownish color found in _floridanus_, differ from the color of typical specimens of both _intermedius_ and _floridanus_, but the average is nearer that of _floridanus_ than that of _intermedius_. Color of pre-adult pelage in the one July-taken young of the year resembles the color of adults. An August-taken young of the year is in process of acquiring the adult pelage but the hairs have not reached their full growth; it is pale yellowish but not so grayish as the other specimens. All characters considered, the specimens from eastern Texas resemble _floridanus_ more than they do _intermedius_, and so are provisionally assigned to _floridanus_ (as was done by Taylor and Davis, 1947:19; Eads, _et al._, 1956:440; and, Davis, 1960:59). Additional material from southeastern Texas is needed. It will be remembered that the type locality of _intermedius_ is in the Rio Grande Valley; all specimens seen, in the study here reported on, from the Texas side of the valley are unquestionably referable to that subspecies.

Intergradation, then, occurs between _L. intermedius_ and _L. floridanus_ in some degree in southern Louisiana and in more marked degree in southeastern Texas. Specimens from the area of intergradation vary more individually in many features than do specimens from other areas. In general the intergrades tend to resemble _floridanus_ in small size externally and _intermedius_ in large size of skull. The specimens from southeastern Texas differ from typical specimens of both subspecies in color, being pale yellowish-gray (instead of yellowish to yellowish-orange as in _intermedius_ or yellowish brown to brownish-gray as in _floridanus_), and this difference is shared to some extent with animals from Louisiana, the latter being somewhat intermediate between bats from Texas and those from Florida and Georgia, although nearer those from Florida and Georgia.

An hypothesis to account for the variation noted is that in Wisconsin Time, and perhaps in earlier Pleistocene times, this yellow bat was (as it is now) a warmth-adapted animal as Blair (1959:461) would term it. Some cool period forced the mainland populations of the two species into two refugia--peninsular Florida and eastern México--and the present area of intergradation is, therefore, of a secondary rather than a primary type. Possibly also the relatively treeless area of part of southern Texas has made for a sparse population there of _Lasiurus intermedius_ and gene flow now may be, and long may have been, slight between the eastern and southern segments of the species.

It could be contended that the peculiar coloration of specimens from southeastern Texas, coupled with the tendency to have a large skull (as has _intermedius_) and small external dimensions (as has _floridanus_), justifies subspecific recognition for the animals that here are termed intergrades. But, judging by the specimens now available, such subspecific recognition would tend to obscure rather than clarify the geographic variation noted.

_Life History_

Probably bats of the species _Lasiurus intermedius_ seek retreats primarily in trees (see Moore, 1949_a_:59-60) but Baker and Dickerman (1956:443) reported "approximately 45 yellow bats" concealed on July 22, 1955, "among dried corn stalks hanging from the sides of a large open tobacco shed" in the state of Veracruz. Young are born in late spring, three being the only number known except that Davis (1960:59) was told that in the vicinity of Mission, Texas, two was the usual number "born in May and June." Sherman (1945:194) reported a female with young (number not given) taken on June 7, 1918, at Seven Oaks, Florida, and another with three young taken on June 20, 1941, at Ocala, Florida. Lowery (1936:17) recorded a female, having three young, obtained on June 17, 1932, at Baton Rouge, Louisiana. A specimen taken on May 19, 1940, at Baton Rouge contained three embryos. Baker and Dickerman (_loc. cit._) reported four adult females from Veracruz as lactating on July 22, 1955, but they were accompanied by flying young of the year and probably were near the end of the lactation period. Among specimens examined, juveniles are available by date as follows: 5