THE WASMANN JOURNAL OF BIOLOGY

VoL. 18, No. 1 SPIUNG, 1960

A Third Luminous M illiped, Motyxia tiemanni, n. sp. (Xystodemidae: Polydesmida)

NELL B. CAUSEY, Fayetteville, ATkansas.

1'he phenomenon of luminescence is known to occur in only three species of millipeds, of which all are North American mem­ bers of the family Xystodesmidae. It could be a character of some other little-known species, for most of them were collected during dayligenus, o topoty1 es should be collected and the species redescribed. Its luminescence was reported to be whitish, "more marked at one time than another," and the source to be round, yellow areas about 1 mm. in diameter, of which there is one near the lateral margin of the dorsal sur­ face of each paranotum; in the darkness, the animal resembles a "double series of small beads of fire . . . crawling about among the dead leaves" (Kenyon, 1893 ). In the other two luminescent species, Luminod e sm1~s sequoiae Loomis and Davenport and Motyxia tienwnni, new specie , the body surface, the legs, and the antennae glow with a constant greenish white light. Davenport, Wootton, and Cushing (1952) found that the luminescence appear in L . sequoiae immediately after hatching and is present even when the larvae are molting. They suggest that the source of it is possibly in the deeper integu­ mentary layers. [ 131 ] 133 THE W ASMANN JOURNAL OF BIOLOGY, Vol. 18, 1960

Lurninodesrnus sequoiae is known only from the type locality, Camp Nelson, Sequoia ational Forest, Tulare Cmmty, Califor­ nia. Luminescent larvae of uncertain position have been collected at Kaweah, which i · 30 miles north of Camp Nelson (Loomis and Davenport, 1951). The generic position of L. seqtwiae is prob­ lematic: on the basis of the somatic and econdary sexual charac­ ters it should go into the genus Motyxia, but on the basis of the four-pron()'ed o-onopods it seems to belong in Xystocheir. Loomis and Davenport (1951) set up the genus Lurninodesrnus for it, but Chamberlin and Hoffman ( 1958) rejected this genus and moved "sequoiae" to X ystocheir. I have never seen it. Its position prob­ ably will not be satisfactorily solved until a 'tudy of the 20 Cali­ fornia species assigned to the closely related genera Cheir-auxus, Arnplo cheir, Delo cheir·, Lurninodesmus, Motyxia, and Xystochei'r has been made. Too little attention has been given to the somatic characters and the probable homologies of the prongs of the gono­ pods of most of these species.

Motyxia tiemanni Causey, new species.

(Figures 1 and 2.)

DIAGNOSIS. A luminescent species distinguished by the details of the gonopods, especially the nearness of the prongs to each other; the seminiferous prong is spinous and slightly curved, and the other two are longer, expanded, flattened, and directed cephalad. TYPE LO ALI'l.'Y. Shirley Meadows, Sequoia ational Forest, Kern County, California. The area of greatest concentration is at an altitude of about 6,700 feet, in deep humu · t hickly shaded by ferns, Ribes sp., Pseudotsuga sp., other conifers, and black oaks. Two collections with a total of about 75 mature specimens were made in l\Iay and in November, 1959, by Mr. Darwin Tiemann. Most of the specimens in the May collection were male ·. In the November collection, females, most of which were gravid, greatly outnumbered the males. TYPE SPECIMEN·. Male holotype and female paratype: Ameri­ can Museum of Natural History, ew York. Male and female paratypes: U. S. ational Museum; University of California, A THIRD LUMINOUS MILLIPED-CAUSEY 133

Berkeley; California Academy of Sciences, San Francisco; Flor­ ida State Plant Board, Gainesville.

DE CRIP'l.'ION OF MALE HOLOTYPE. Greatest body width 5.6 mm., length about 30 mm. Dorsum light yellow, shading to orange on the paranota; prozonites grayish yellow; black middorsal line intermittent; head, antennae, legs and venter cream color. All body surfaces and appendages except the sterna and the gonopods are luminescent; the luminescence is brightest on the thickened lateral margins of the paranota and weakest on the prozonites. The collum is slightly narrower than the tergite of the second seg­ ment; both the anterior and posterior margins are rounded, and the lateral angles are depressed slightly and broadly rounded. Segments 2, 3, and 4 have the paranota, directed obliquely for­ ward, those of segments 5 through 15 project laterad, and from segments 16 through 19 they are caudally directed. Paranota of middle body segments are about as wide as they are long, and the two lateral angles are rounded almost equally. Space between paranota about one-half the length of the paranota in life. Caudal angles of all paranota rounded. Paranota of segment 19 very small, exceeded by the paranota of segment 18. Caudal tergite straight, narrowly truncated. Dorsum slightly arched, the para­ nota of all segments continuing the slope of the dorsum. Beginning with the first segment, there are a very few indistinct, scattered pustules; progressing caudad, the pustules are more numerous, especially along the caudal margin of the metazonites; they are most numerous on segment 16, where there are about 18 in the marginal row and about that many more scattered irregularly on the metatergite. Legs slender, with the prefemoral spines hooked and the longest ones about half the length of the prefemurs; no coxal spines. Sterna broad, ·mooth, with a slight indication of a sternal peg adjacent to the second legpair of mo t diplosomites. Between the third pair of legs there is a pair of short sternal pegs; the coxal segment of these legs is slightly enlarged on the mesial surface. Between the fourth pair of legs there i · a pair of longer, broader, triangular sternal processes; the coxal segment of these legs has no lobe. In situ the gonopods are directed cephalad and are contiguous along the midbody line, where they lie flat in a depression in the sterna of the fifth and sixth segments. The mesiodorsal prong, or 134 THE WASMANN JOURNAL OF BIOLOGY, Vol. 18, 1960 the prefemoral branch, is rounded at the apex and broader and slightly longer than the ectoventral prong, or tibiotarsus (fig. 1). A small lobe at the base of the ectoventral prong (fig. 2) possibly is homologous with the fourth prong of L. sequoiae. The spinous prong is the solenomerite.

l?EMALE PARA'l'YPE. Greatest body width 6.8 mm., length about 36 mm. Somatic characters as in the male except that the dorsum is more highly arched, the paranota are slightly smaller, the para­ nota of segments 2, 3, and 4 are bent forward a little more, the

Figure 1. Right gonopod of male holotype of Motyxia tiemanni, mesial view. (Setae omitted.) Figure 2. Subectal view of same. A THIRD LUMINOUS MILLIPED-CAUSE1' 135

sterna are a little broader, and the legs are slightly shorter and thinner. Between the third pair of legs there is a pair of small, triangular sternal lobes. Third sternum with no median lobe on the margin of the vulvar opening. Vulvae relatively small, thickly setose. and without a fing·erlike lobe. VARIATIONS. Body width varies from 5 mm. to 6.1 mm. in the male and from 6 rom. to 7 mm. in the female. There is also some variation in the ·ize of the sternal processes anterior to the gono­ pods. The nineteenth segment may be almost completely covered by the eighteenth.

REFERENCES CITED

CH.UIBERLI •, R. V., and RICHARD L. HOFFlliAN 1958. Checklist of the millipeds of North America. U. S. National Museum Bulletin, 212:1-236. DAVENPORT, DEMOREST, DONALD M. W001"1'0N, and JOHN E. C USHING 1952. The biology of the Sierra luminous milliped, Luminodesmus sequoiae, Loomis and Davenport. Biological Bulletin, 102 (2) :100- 110, 4 figs.

KI~ NYON, FREDERICK C. 1893. A preliminary list of the Myriapoda of Nebraska, with de­ scriptions of new species. Publications of the Nebraska Academy of Science, 3:14-18. LOOllfiS. H. F., and DElliOHES'l' DAVENPOll'l' 1951. A luminescent new xystodesmid milliped from California. Journal of the Washington Academy of Science, 41(8) :270- 272, 1 fig.