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1954

The Lepidopterists* News

131

SIZE OF PAPILIO GLAUCUS IN MISSISSIPPI by Bryant Mather

A consideration of a limited amount of information on Papilio glaucus L. in Mississippi suggests that the population represented there is generally similar to that described from the District of Columbia (Clark, 1932) and from Virginia (Clark & Clark, 1951). Specimens assignable to P. glaucus australis Maynard, reported from "the Southern States" (Holland, 1947) and from "Georgia through Florida and Gulf States" (Klots, 1951), have not been found. A series of four males and two females was examined by Mr. C. F. DOS Passos and determined as Papilio glaucus glaucus. No yellow females (form "turnus") are known to have been found in Mississippi; none were found in the collection at Mississippi State College when it was examined by the writer in March 1953- It is therefore assumed that the statement by HUTCHINS (1933): "Papilio glaucus L. Uncommon. Papilio glaucus turnus L. Very common," must refer to the occurrence of yellow males and dark females. Mr. and Mrs. Hans Epstein report {in litt.) that no yellow females are known to them to have been found in Alabama. The very small spring individuals previously reported from "as far south as the mountains of North Carolina" (Clark & Clark, 1951) and from Kansas (Field, 1938), occur at least as far south as central Mississippi.

The series of twenty specimens in the writer's collection has been examined (other Mississippi specimens known to exist but which were not examined include those in the collection at Mississippi State College, five in the collection of C. F. DOS PASSOS, and one in the collection of Dr. FRANK MORTON Jones taken by him in Biloxi in the spring of 1910). Two dimensions of each specimen were measured : wingspread and forewing length. The measurements were made using dividers, opened to the dimension being measured and then placed against a millimeter scale. Wingspread is the dimension indicated by WOHLFAHRT (1952) as "Spannweite". Forewing length, the dimension used by Clark (1932) and Clark & Clark (1951), is the distance from the base to the apex of the forewing, and presumably is the dimension referred to by Brown (1951) as the "greatest radius of the forewing." These data are given in Table II, and some of their relations are indicated graphically in Fig. 1. For these twenty specimens, the ratio of wingspread to forewing length varies from 1.50 to 1.77; the average is 1.63. Both the specimen with the 1.50 ratio and that with the 1.77 ratio are females. Fig. 1 indicates that there appears to be no tendency for the ratio to change with change in forewing length, with season, or with sex. The tendency for size to increase from spring to fall, and the tendency for females to be larger than males, are clearly indicated. No correlation is indicated between size and section of the state in which taken. Since the series includes only one specimen from the Gulf Coast, the possibility that a significantly different population, perhaps assignable to P. glaucus australis, occurs there remains to be investigated.

132                                          Mather: Papilio glaucus Size                            Vol.8: no.5

Information on the size range of P. glaucus is given in Table I. In all references except Clark (1932) and Clark & Clark (1951) the dimension given is "expanse." Reported values for expanse in inches have been converted to expanse in millimeters by multiplying by 25.4 and from expanse in mm. to forewing length in mm. by the formula:

Forewing length = 0.5 (expanse — 4).

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FoReWWG LENGTH, TY,m (x)

Fig. 1. Measurement relations of 20 P. glaucus from Mississippi.

The smallest length indicated by the references is 36 mm., the greatest 80 mm. (the greatest indicated in any reference other than Klots is 69 mm.); the extremes of the twenty Mississippi specimens are 36 and 68 mm. It is therefore suggested that the size range of P. glaticus in Mississippi is as great as is the size range of the species in the entire United States, except Florida. The Clarks (1951) report Florida females with forewings up to 76 mm. in length; Klots (in litt.) refers to a yellow Florida female with a forewing length of 81 mm. as "not the largest I have seen."

It is extremely unlikely that the present series includes the extremes of size that occur in Mississippi, but it is believed also unlikely that specimens

1954

The Lepidopterists' News

133

materially smaller than the smallest included here will be found. Further collecting would provide confirmation of these assumptions. A larger, statistically more significant, series would permit calculations of frequency distribution by size, and, together with similar data from other areas, would permit comparisons between populations.

TABLE I. Forewing length, mm. (reported or computed)

Reference                                    Range Min.        Max. Min.-Max. Min.-Max.

Males       Females

As was noted above, all the references to size except those by the Clarks are to expanse. In none of them is a definition of expanse given. The following definition is given by Field (1938): "Expanse: the distance between the apices or other widest point of the wings when fully spread." The term "fully spread", as used in this definition, could have more than one interpretation. Klots {in litt.) states that the values given in the Field Guide (1951) refer to "wing expanse, obtained by adding the width of the thorax to two times the forewing length." This is an entirely clear definition and agrees with that indicated diagramatically for "Flugspanne" by WOHLFAHRT (1952). I fail, however, to see advantages to the use of expanse as the basic measure of butterfly size. The determination of expanse requires measurement and summation of two dimensions. Wingspread, involving measurement from the apex of one wing to that of the other, is not reliable, because it will vary depending on the spreading of the insect. Following length is a single, reliable, easily determined dimension and would seem to be the most useful.

A number of authors state dimensions in the style "3-00 to 4.25 in." It is doubted that the apparently indicated accuracy or precision to the nearest 0.01 in. is intended. If by "3.00" is meant "nearer 3 than 2% or 3V4" and if by "4.25" is meant "nearer 4V4 than 4 or 4Vi"; then it would be more accurate and distinctly preferable to write "3 to 4)4". It is misleading to write "3.00" unless it is intended to imply that the true value is greater than 2.995 and less than 3.005 (Simpson & Roe, 1939: p. 25). It would, of course, be much better to obtain and report such data in millimeters.

A series of as few as twenty specimens may provide the basis for tentative conclusions about certain significant characteristics and relations of the population sampled, provided that the series is considered as a sample and the conclusions are restricted to those justified by the sample. Extreme variants in a sample of any size should neither be ignored as freaks nor regarded as great prizes. They have equal significance with more typical specimens in giving the complete picture of the population of which they are members.

134                                          MATHER: Papilio glaucus Size                            Vol.8: no.5

TABLE II. Data on Twenty P. glaucus from Mississippi

N=North, C=Central, S=South [Moss Point (S) to Glen (N) = 300 miles]

References

Brown, F. Martin, 1951. Simple Statistics for the Taxonomist—I. Lepid. News 5: 4.

Clark, Austin H., 1932. The butterflies of the District of Columbia and vicinity. U. S. £___Nat. Mus. Bull. 157: 179-189.

. . . .-j.. & Leila F. Clark, 1951. The butterflies of Virginia. Smithsonian Misc. Coll. \        116, no. 7: 124-144.

ElrodTMorton J., 1906. The butterflies of Montana. Univ. Montana Bull. 30: 174 pp.

Field, William D., 1938. A manual of the butterflies and skippers of Kansas. Bull. Univ. Kansas 39, no. 10: 210,291.

Haydon, Stansbury, 1933. The Papilionida? of Maryland. Proc. Nat. Hist. Soc. Maryland 2: 14 pp.

Holland, W* J., 1947. The butterfly book. 424 pp. Doubleday & Co., Garden City, N.Y.

Hutchins, Ross E., 1933. Annotated list of Mississippi Rhopalocera. Canad. Ent. 65_: 210-213-

Klots, Alexander B., 1951. A field guide to the butterflies: p. 175. Houghton Mifflin \_____£p., Boston.

Macy, Ralph W. & Harold H. Shepard, 1941. Butterflies. 247 pp. Univ. Minnesota Press, Minneapolis.

Saunders, Aretas A., 1932. Butterflies of the Allegany State Park. N.Y. State Mus. Handb. I         13: 270 pp.

Simpson, George Gaylord & Anne Roe, 1939. Quantitative zoology: p. 25. McGraw-Hill, New York.

Wild, William, 1939. The butterflies of the Niagara Frontier Region. Bull. Buffalo Soc. Nat. Set. 19, no. 1: 55 pp.

Wohlfahrt, Th. A., 1952. On the value of little noticed characters for the classification of the Lepidoptera. Lepid. News 6: 13-27, 9 figs.

P.O. Drawer 2131, Jackson, Miss., U. S. A.