University of Kansas Publications
Museum of Natural History

Volume 14, No. 5, pp. 73-98, 4 figs.
December 29, 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.

University of Kansas
Lawrence
1961

University of Kansas Publications, Museum of Natural History

Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Theodore H. Eaton, Jr.

Volume 14, No. 5, pp. 73-98, 4 figs.
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

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 grayishL. 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 IslandsL. 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 mmL. 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 moreL. intermedius.
•  
• 10'. Total length less than 119 mm.; length of upper tooth-row less than 6.0 mmL. ega.

Lasiurus intermedius

Northern Yellow Bat

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, 1949a: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 mi. N Baton Rouge, Louisiana (June 26, 1953); Palm Beach, Florida (July 6, 1950); and Izamal, Yucatán ("taken with mother" on July 28, 1910). Breeding probably takes place in autumn and winter; Sherman (op. cit.:196) reported males from Florida as sexually "mature" from the beginning of September to mid-February. Late winter segregation of sexes has been reported.

Subspecies

In the following accounts, localities of occurrence in each state are listed from north to south; if two lie in the same latitude, the westernmost is listed first. Localities that are italicized are not shown on the distribution map (Fig. 2), either because undue crowding of symbols would result or, in several cases, because we could not precisely place the localities. Length of forearm is the average of both forearms in individuals in which both forearms could be measured.

Lasiurus intermedius intermedius (H. Allen)

Lasiurus intermedius floridanus (Miller)

Lasiurus intermedius insularis, new subspecies

Black dots represent localities of capture of specimens examined. Hollow circles represent localities of capture of other specimens recorded in the literature but not examined by us (Hall and Jones).

Remarks.—Four of the five specimens on which the name L. i. insularis is based differ to such a degree from mainland populations of the species L. intermedius that specific rather than subspecific recognition for the Cuban bat might seem warranted. It is because of the fifth specimen (USNM 254714) that we accord subspecific rank to insularis. It is smaller than the other Cuban specimens and except for longer condylocanine length, longer mandibular tooth-rows, narrower interorbital region, and heavier dentition is indistinguishable in measurements from the largest specimens of L. i. intermedius from the mainland. In addition, it appears not to have the enormously developed sagittal crest of the other specimens of insularis although posteriorly the dorsal part of the skull (where the crest is most prominent) is missing. USNM 254714 agrees with the other Cuban specimens in having the mesostyle of M1 and M2 somewhat reduced and in having a small M3 on which the cingulum and second commissure are poorly developed, and this specimen is regarded as representative of the lower size limits of the Cuban population.

The skull from San Bias was found in an owl pellet (see de Beaufort, 1934:316).

Table 1.—Cranial Measurements (in Millimeters) of Three Subspecies of Lasiurus intermedius