William H. Piel.
The Nearctic jumping spiders of the genus Admestina (Aranaeae: Salticidae).
Psyche 98:265-282, 1991.

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PSYCHE
Vol. 98 1991 No. 4
THE NEARCTIC JUMPING SPIDERS OF THE GENUS ADMESTINA (ARANEAE: SALTICIDAE).*
Museum of Comparative Zoology, Harvard University Cambridge, Massachusetts 02 138
The genus Admestina contains three Nearctic species. A southern species, A. archboldi, occurs between the 25th and 30th parallels and runs west to Texas. A northern species, A. wheeled, is found along the 45th parallel and stretches west to North Dakota. A third species, A. tibialis, spans the gap in between- from Florida to Connecticut (Map 1).
These jumping spiders are small, less than 4.5 mm in length. The smallest species, A. archboldi, is between 2 and 3 mm. Speci- mens are collected by beating branches of pine, willow, elm, oak, and chokecherry. Alternatively, sweeping bark with a soft brush can dislodge them from within crevices (pers. comm., Robert L. Edwards).
Very little is known of their biology or behavior. Females have been found guarding egg sacs, containing between 4 and 19 eggs. The egg sacs have been found under bark, and in one case, in a gall on an oak tree. Their small size and flattened prosoma allow these spiders to hide by squeezing into narrow gaps, which may explain why so few have been collected.
*Manuscript received 5 September 1991.
265




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266 Psyche [VOI. 98
METHODS AND MATERIALS
The following museums graciously loaned the spiders necessary for this study, whose curators I thank for their assistance: AMNH
FSCA
MCZ
USNM
ZMB
American Museum of Natural History, NY, N. Plat- nick, L. Sorkin;
Florida State Collection of Arthropods, FL, G. B. Edwards;
Museum of Comparative Zoology, MA, H. W. Levi; National Museum of Natural History, Smithsonian Institution, Washington, D.C., J. Coddington; Zoologishes Museum an der Humboldt Universitat, Berlin, M. Moritz.
I would like to thank T. Eisner for his photograph as well as H. W. Levi, W. P. Maddison, and an anonymous reviewer for com- menting on the manuscript. Thanks also go to E. Brainerd for the use of her digitizer.
At least one specimen from each locality was photographed with a Panasonic@ WV-1500X video camera attached to a com- pound microscope. The camera fed analogue video signals into a VTR monitor to assist in focussing. Images were captured using a MacVisionTM digitizer and stored on a MacintoshTM computer. The computer allows relatively inexpensive pictures to be rapidly reproduced on sheets of paper using a dot-matrix printer. Thirty-three of these printed sheets of male spiders were spread across a large table. Each sheet depicted three pictures of the same specimen: a lateral view of the palp; a dorsal view of the prosoma; and a lateral view of the first leg. Observing all specimens simulta- neously allows them to be easily grouped according to similar appearance. Traits important to differentiating species can be dis- tinguished from those that correspond to mere intraspecific varia- tion. The technique used here is analogous to placing all specimens under the microscope and studying their anatomical differences concurrently.
The males were resolved into three different species and the corresponding females were studied in order to uncover their dis- tinguishing anatomical traits. Although A. tibialis was separated from the rest, the intraspecific variation within these remaining



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females made it difficult to distinguish A. wheeleri from A. archboldi. Unraveling this problem demanded clearing the copula- tory organs with Hoyer's medium and drawing spermathecal ducts. The width of the epigyna and pedipalps and the length of the leg articles were measured using a microscope with a built-in reticule. The length of a leg article was taken from its most distal points. When measuring pedipalps, care was taken to ensure that all palps rested in the same position in order to reduce measurement error. Palps were arbitrarily deemed at a proper angle when the tibia1 apophysis appeared flat and a vertical line on the reticule ran through the center of the embolus and passed to the left of the palp's posterior point (see dotted line in figure on Map 2a). The geographic variation in genital width was best understood using MapMakerTM software to chart relative sizes over a map of the United States (Map 2).
RESULTS AND DISCUSSION
The three species of Admestim distinguish themselves almost entirely on the structure of their genitalia: A urchboldi, A. wheeleri, and A. tibialis. The last species was first described by Koch (1848), based on a male specimen from Pennsylvania which is presently in such poor condition that it cannot be identified with certainty. Later A. wheeleri was described from Wisconsin, but synonymized with A. tibialis shortly thereafter (Peckham and Peckham, 1888, 1894, 1909). Given the state of disrepair of Koch's holotype, it is difficult to evaluate the validity of Peckham's syn- onymy. For what is largely a matter of convenience, I have opted to presume that Koch's original specimen was not the species described by the Peckhams. Notice that A. wheeleri has never been collected in Pennsylvania, and the geographic ranges of the two species suggest that one is slightly more likely to find A. tibiulis in this state. Thus the name A. wheeleri should be retained. It remains difficult to distinguish A. archboldi from A. wheeleri because their anatomical differences are barely noticeable. The embolus on the palp of A. archboldi spirals more sharply than that of A. wheeleri, and the cymbium of the former is relatively smaller. When cleared in clove oil, the palps reveal slight differ- ences in the design of their seminal ducts (Figs. 9, 16). Cleared



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268 Psyche [Voi. 98
epigyna show differences in the relative shape of their spermathe- cae (Figs. 7, 8, 12-15).
Probably the most striking difference between the two species is their size disparity: the southern species resembles a miniature replica of the northern. Arguably, these two forms may constitute one species which restricts its appearance to the two extreme ends of a putative geographic cline. Geographic variation exhibiting an increase of size with latitude is common among many inverte- brates, as the rabbit tick Haemaphysalis ieporispalustris exempli- fies (Thomas, 1968).
However, if A. archboldi and A. wheeleri constituted a single species with clinal variation, then I would expect its sister species, A. tibiatis, to show the same geographic trend. This corresponding trend is expected because presumably the latter species, which is morphologically similar to the former, submits to approximately the same set of selective pressures as its closest sister species. In fact, A. tibiaiis shows no such clinat variation. Neither males nor females south of North Carolina show significant differences in genital width or length from those north of North Carolina. In contrast, the same parameters in A. archboldi are significantly Plate 1. Atiiiie!,!inu firdilwlili. I'emalc fpho~o T. Eisner).



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smaller than in A. wheeleri (p < 0.001; see Appendix, Table 1 and Map 2). These parameters carry particular importance because differences in genital size are more likely to ensure reproductive isolation than differences in other body parts. Thus, I am led to believe that A. archboldi and A. wheeleri are separate and distinct species.
Admestina Peckham and Peckham
Plate 1
Admestina Peckham and Peckham, 1888: 78. Type species by monotypy, A. wheeleri Peckham and Peckham, 1888. The gen- der of the generic name is feminine (Bonnet, 1955: 158). Diagnosis. The tibia of leg I is thickened in both sexes and has no more than 1 ventral macroseta. The ocular quadrangle is less than half the length of the distinctly flattened prosoma. The ante- rior end of the sternum narrows to a blunt point. Description. The prosoma in Admestina is elongated and dorso- ventrally flattened. Its width is between 112 and 213 the length of the prosoma at 213 along its length from the anterior end. The width at this point falls between 112 and 213 the length of the pro- soma. The median furrow is inconspicuous and located particularly far from the eye quadrangle. All species have a single tooth on the retromargin of the chelicerae and two (with the larger located dis- tally) on the promargin.
Anterior median eyes are subcontiguous. The distance between the posterior median eyes corresponds to almost twice that separat- ing these eyes and the anterior lateral eyes. The distance separating the posterior median eyes and the posterior lateral eyes equals or is slightly greater than the distance separating the latter and the ante- rior eye row.
The dorso-ventral thickness of the tibia on leg I is generally 314 its length, although this value varies anywhere from 213 to 516. This same leg is always the stoutest, and its tibia in females may or may not have a single ventral macroseta. Males almost never have this macroseta. The legs of a live spider are almost translucent, with black annuli distal to each joint. In alcohol the translucence turns into an opaque white or yellow.




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270 Psyche [vo~. 98
The opisthosoma is longer than the prosoma, especially in gravid females. Its dorsal surface has a conspicuous scutum in the males of A. tibialis and A. wheeleri, although the markings remain approximately the same in both sexes of all species: white with a median black band that is broken into at least six lateral branches (Plate 1). This pattern is not unlike that found in Pityohyphantes (Linyphiidae).
The black prosoma appears gray when dry because it is covered with white pubescence. This covering is uniform, with the excep- tion of two denser collections of setae that form white spots and are located just medial to the posterior median eyes. Under alcohol the prosoma turns reddish brown, except for the ocular area, which remains dark brown to black.
Natural History. Little is known of Admestina's behavior. Although a male has been gathered walking on the ground at night, specimens are generally collected by beating branches. Females lay few eggs (4 to 20) in a particularly narrow retreat constructed within a crevice on the bark of a tree.
Misplaced Species. Galiano (1987) moved Admestina bitaeniata Simon, 1902: 28, male, into a new genus called Admesturius. Additionally, she moved Admestina insularis Banks, 1902: 66 into the genus Helvetia (Galiano, 1989).
Key to Admestina species
1 Male embolus about twice as long as thick (Fig. 3). Female openings large, about twice their diameters from the genital groove (Fig. 4) ............................................................. ..tibialis -
Male embolus about four times as long as thick (Figs. 2, 6). Female openings smaller, about four times their diameters from the genital groove (Figs. 1, 5) ......................................... 2 2(l)Male palp wider than 0.2 mm (Map 2a) or female epigynum wider than 0.33 (Map 2b) ............................................ wheeleri -
Male palp narrower than 0.2 mm or female epigynum narrower than 0.33 .................................................................... archboldi



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272 Psyche
[Vol. 98
Admestina tibialis (Koch)
Figures 3, 4, 10, 1 1 ; Map 1
Maevia tibialis C. L. Koch, 1848: 78, m. holotype from Pennsylvania in ZMB, examined. Roewer, 1954: 11 85. Bonnet, 1955: 159.
Diagnosis. The female is easily distinguished by the enlarged openings of her epigynum (Figs. 4, 11). The male palp carries a thickened embolus (Fig. 3), which corresponds with the female's enlarged epigynal openings. The dorsal surface of the male's abdomen has a scutum that is more heavily sclerotized than in either of the other Admestina species.
Description. A female specimen from Pennsylvania measured 3.8 mm in total length. The prosoma was 1.4 mm, 0.8, and 0.72 in length, width, and height respectively. The following describes the length of her leg segments in millimeters: I I1 I11 IV
Femur 0.56 0.48 0.48 0.65
Patella 0.38 0.28 0.24 0.32
Tibia 0.36 0.28 0.3 1 0.42
Metatarsus 0.20 0.20 0.24 0.32
Tarsus 0.23 0.22 0.24 0.32
The female always has one ventral macroseta on tibia I. A male specimen from Pennsylvania measured 3.1 mm in total length. The prosoma was 1.3 mm, 0.8, and 0.6 in length, width, and height respectively. The following describes the size of his leg segments in millimeters:
I I1 I11 IV
Femur 0.57 0.46
0.46 0.66
Patella 0.40
0.28 0.22 0.3 1
Tibia 0.38 0.30
0.30 0.40
Metatarsus 0.20 0.19
0.24 0.3 1
Tarsus 0.24 0.22 0.24 0.26
Natural History. Specimens in Florida have been collected from pine trees. A female in Connecticut was found guarding her egg



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sac hidden in the bark of an elm tree. The sac contained 4 eggs (Kaston, 1948). Females have been collected between March and September. Males are mostly found between August and December (Fig. 10, Ring 2).
Distribution. Eastern United States from Connecticut to Florida (Map 1).
Records. CONNECTICUT: Westville, 23 June 1938, f. (D. S. Riggs, USNM). Branford, 1940, 15 June 1936, f. (B. J. Kaston, USNM). NEW YORK: Orient Beach State Park, 23 Sept. 1962, f. (W. Ivie, AMNH); Sea Cliff, m., f. (N. Banks, MCZ). PENNSYLVANIA: Bucks Co., Horseshoe Bend, Neshaminy Creek NE of Jamison, 15 June 1957, m., f. (W. Ivie, AMNH). MARY- LAND: Bay Ridge, m. (N. Banks, MCZ). VIRGINIA: Falls Church vial, m. (N. Banks, MCZ); Falls Church, m. (R. V. Chamberlin, MCZ); Revell's Island, 18 June (R. V. Chamberlin, MCZ). TEN- NESSEE: Stony Point, 20 Aug. 1939, m. (R. V. Chamberlin, AMNH). LOUISIANA: Baton Rouge, f. (N. Banks, MCZ). FLORIDA, Alachua Co., Gainesville: 22 Nov. 1926, m. (AMNH); Lake Alice, hanging from pine tree, 25 Oct. 1978, m. (G. B. Edwards, FSCA); 14 Apr. 1984, f. (G. B. Edwards, FSCA); potted plant under oak, 28 Nov. 1975, m. (J. C. E. Nickerson, FSCA); Dunedin, 15 Mar. 1927, m., f. (W. S. Blatchley, MCZ); St. Lucie Co., Bluefield, on Pinus sp., 14 Aug. 1983, m. (K. Hibbard, FSCA).
Admestina wheeleri Peckham and Peckham
Figures 1, 2, 7, 8, 10; Map 1, 2
Admestina wheeleri Peckham and Peckham, 1888: 78, pi. 1, fig. 58; pi. 5, fig. 58, m. holotype from Wisconsin in MCZ, exam- ined. Banks, 1892; 78, pi. 2, fig. 34, f. Peckham and Peckham, 1894: 120, pi. 11, fig. 6, m. Emerton, 1909: 227, pi. 11, fig. 6, f. Admestina tibia1is:- Peckham and Peckham, 1909: 510, pi. 42, fig. 3-3b, m., f., incorrect synonymy. Kaston, 1948: 472, pi. 94, figs. 1740-1744, m., f. Roewer, 1954: 1185. Bonnet, 1955: 159. Diagnosis. The female has an epigynum with smaller openings than A. tibialis (Fig. 1, 7-8), and is distinguished from A. arch- boldi by its larger size (Map 2). Cleared epigyna reveal two coils of spermathecal ducts. The relative size of these compared with the



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274 Psyche [VOI. 98
Figures 1-2, Admestinu wheeleri Peckham and Peckham. 1, epigynum, ventral. 2, palp, retrolateral.
Figures 3-4, Admesiina tibialis (Koch). 3. palp, retrolaterai. 4, epigyniim, ven- tral.
Figures 5-6, Admesttna urchboldi new species. 5, epigynum, ventral, 6, palp, retrolateral.
Scale he, 0. \ ram.




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separation of the epigynal openings proves to be greater than that of A. archboldi. The male palp is larger than that of A. archboldi (Map I), and carries a thin, needle-like embolus (Fig. 2). The dor- sal surface of his abdomen has a scutum that is less heavily sclero- tized than in A. tibialis.
Description. A female specimen from Wisconsin measured 4.3 mm in total length. The prosoma was 1.5 mm, 1.0, and 0.7 in length, width, and height respectively. The following describes the length of her leg segments in millimeters: I I1 111 IV
Femur 0.64 0.52 0.53 0.7 1
Patella 0.4 0.33 0.26 0.39
Tibia 0.36 0.33 0-35 0.52
Metatarsus 0.24 0.24 0.28 0.38
Tarsus 0.25 0.25 0.28 0.3 1
The female may or may not have one ventral macroseta on tibia I. The occurrence of this feature varies from population to popula- tion, although most lack this macroseta. A male specimen from Ithaca measured 3.3 mm in total length. The prosoma was 1.4 mm, 0.9, and 0.6 in length, width, and height respectively. The following describes the length of his leg seg- ments in millimeters:
I I1 I11 IV
Femur
0.67 0.5 1 0.54 0.69
Patella
0.42 0.3 0.27 0.32
Tibia 0.46 0.35
0.32 0.46
Metatarsus 0.23 0.21 0.24 0.32
Tarsus
0.24 0.24 0.26 0.28
The male always lacks macrosetae on tibia I. Natural history. Wallace collected an egg sac from Michigan containing 19 eggs. Spiders have been collected following the beating of willow, dead oak, and dead chokecherry branches in North Dakota. Females can be gathered between May and August. Males are collected between July and September (Fig. 10, Ring 1).



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Psyche [Val. 98
Figures 7-8, Admestina wheeleri Peckham and Peckham, cleared epigyna, ven- tral. 7, specimen from Wisconsin. 8, specimen from Massachusetts. Figure 9, Admestina tibialis (Koch), cleared palp, prolateral. Figure 10, Seasonal occurrence of Admestina Peckham and Peckham. Squares, males. Circles, females. Ring 1, Admestina wheeleri Peckham and Peckham. Ring 2, Admestina tibialis (Koch). Ring 3, Admestinu archboldi new species. Figure 11, Admestinu tibialis (Koch), cleared epigynum, ventral. Figures 12-15, Admestinu archboldi new species, cleared epigyna, ventral. 12, specimen from Louisiana. 13, specimen from Florida Keys. 14, specimen from Highlands Co., FL. 15, specimen from Alachua Co., FL. Figure 16, Admestina archboldi new species, cleared palp, prolateral. Scale line, 0.1 mm.




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Distribution. Northern United States and southern Canada; from Maine to North Dakota (Map 1).
Records. ONTARIO: Niagara Co., Long Beach., 10å¡C. 4 May 1975, m. (just molted), f. (W. P. Maddison, FSCA); Turkey Point, 24 Aug. 1956, m., f. (A. M. Nadler, AMNH). MASSACHUSETTS: Middlesex Co., Pepperell, 15 Sept. 1976, m. (H. W. and F. Levi, MCZ); Cambridge, on fences, 4 June 1923, f. (J. H. Emerton, MCZ); Holliston, 10 June 1923, f. (J. H. Emerton, MCZ); Sharon, 9 Aug. 1902, m. (E. B. Bryant, MCZ); Waltham, 26 June 1906, f. (MCZ); Monponsett, 12 June 1912, f. (J. H. Emerton, MCZ). CONNECTICUT: Rocky Hill, 15 Dec. 1948, f. (L. Gonthier, USNM); Meriden, 26 Feb. 1961, f. (J. F. Lienisch, USNM). NEW YORK: Ithaca, f. (E. B. Bryant, MCZ); Ithaca, 31 June 1909, m. (E. B. Bryant, MCZ). MICHIGAN: Muskegon Co., 13 Aug. 1945, m. (Chickering, MCZ); Livingston Co., E. S. George Reserve, 21 Jul. 1954, 22 Jul. 1954, 23 Jul. 1954, 26 Jul. 1954, 23 Aug. 1954, 15 Aug. 1954, 25 Aug. 1951, m.m., f.f. (H. K. Wallace, FSCA); Homer, spruces and pines, 16 Aug. 1933, m. (Chickering, MCZ). WISCONSIN: Jackson Co., Black River Falls by US. 3, 25 June Map 2a. Geographic variation of width of palp in male Admestina wheeleri Peck- ham and Peckham and Admestina archboldi new species. Map 2b. Geographic variation of width of epigynum in female Admestina wheeleri Peckham and Peckham and Admestina archboldi new species.



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278 Psyche [VOI. 98
1966, f. (L. Pinter, MCZ). NORTH DAKOTA: Bottineau Co. Gorge at Bottineau, beating dead oak., 30 Aug. 1962, m. (R. L. Post, R. D. Gordon, AMNH); McHenry Co., 11 Sept. 1963, m. (R. L. Post and R. D. Gordon, AMNH); Benson Co., 14 Aug. 1963, m., f. (R. L. Post, AMNH). SOUTH DAKOTA: Lawrence Co. 5 mi. N Spearfish, 28 Sept. 1968, m. (B. Cutler, FSCA). Admestina archboldi new species
Plate 1, Figures 5, 6, 10, 12-16; Map 1, 2 Holotype. Female holotype from the Archbold Biological Station in Highlands Co., Florida, 26 Mar. 1989 (W. H. Piel) in MCZ. The species is named after the founder of the Archbold Bio- logical Station where the holotype was collected. Diagnosis. The female epigynum looks very much like that of A. wheeleri (Fig. 5). The major difference lies in the relative length of the two spermathecal coils compared to the size and sep- aration of the openings (Figs. 12-15). This parameter is noticeably smaller in A. archboldi. The male genitalia likewise resemble miniature versions of those of A. wheeleri. The embolus differs in shape, being bent somewhat sharper (Fig. 6). From a lateral aspect of the palp one notices that the embolus of A. archboldi protrudes farther relative to the cymbium than it does in A. wheeleri (Fig. 16). Also, the seminal tube seen in cleared palps of A. archboldi shows one less loop (Fig. 16). The dorsal scutum is barely notice- able compared to the other two species.
Description. The female measures 2.5 mm in length. The pro- soma is 1.2 mm, 0.7, and 0.5 in length, width, and height respec- tively. The following describes the length of her leg segments in millimeters:
I I1 I11 IV
Femur 0.47 0.4 0.4 0.55
Patella 0.28 0.24 0-21 0.27
Tibia 0.28 0.26 0.24 0.35
Metatarsus 0.18 0.17 0.2 0.29
Tarsus 0.19 0.18 0.22 0.27
Females have one ventral macroseta on tibia 1-



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The male measures 3.1 mm in length and its prosoma 1.2 mm, 0.2, and 0.6 in length, width, and height respectively. The follow- ing describes the length of his leg segments in millimeters: I I1 111 IV
Femur 0.56
0.44
0.4 0.56
Patella
0.36
0.26 0.21