AMERICAN MUSEUM NOVITATES Published by Number 1298 THE AmFnuICAN MUSEUM OF NATURAL HISTORY September, 28, 1945 New York City SCORPIONS OF THE GENUS HADRURUS THORELL BY HERBERT L. STAHNKE1 HIADRURUS THORELL carapace. Keels poorly developed. An- Hadrurus THORELL, 1876, Ann. Mag. Nat. terior median furrow distinct, while pos- Hist., ser. 4, vol. 17, p. 11; KRAEPELIN, 1899, terior median furrow ends posteriorly as Das Tierreich, Scorpiones und Pedipalpi, no. 8, p. 187; POCOCK, 1902, Biologia Centrali- a deep, narrow pit. A broad furrow leads Americana, Scorpiones, Pedipalpi, Solfugae, p. laterally from each ocular tubercle, making 5; EWING, 1928, Proc. U. S. Natl. Mus., vol. the figure of a cross with the median fur- 73, p. 7; HOFFMAN, 1931, An. Inst. Biol. Mexico, rows. Posterior to this is another trans- vol. 2, p. 334; WERNER, 1934, in Bronn, Klassen und Ordnungen des Tierreichs, vol. 5, book 8, verse furrow which is deep laterally but Pedipalpi, Scorpiones, p. 265. quite shallow and indefinite where it crosses the posterior median furrow. The scorpions of this genus are popularly Coarsely granulated in general. Usually called the giant hairy scorpions. This is the interocular triangle very sparsely because of the large, noticeable bristles covered on female but densely covered rather thickly covering the pedipalps, legs, with medium-sized granules on male. and distal segments of the cauda including the vesicle of the telson. The movable DORSAL PREABDOMEN: Color dependent finger of the chelicera is armed on its on species. No keels present on first six inferior border with a single large, sharp, segments. Median and lateral keels only darkly pigmented tooth. The ocular poorly developed on seventh segment. tubercle is approximately in the middle Terga generally well covered with small to of the carapace. Four species are now large granules, but frequently the posterior recognized in the genus. Their venom is and lateral margins bear the largest ones. not of a lethal nature, even when relatively The seventh segment is more densely large quantities are injected in white rats granulated and bears much larger granules. of only 50-60 grams. In general, labora- Sexual differences are noticeable in granule tory and clinical experiences indicate that size, but the variation in one sex is great the venom apparently produces only a enough to obliterate the value of this factor local reaction consisting of a badly swollen in sex determination. area around the site of the injection which VENTRAL PREABDOMEN: Color depend- may become greatly discolored. The ent on species. Bristles sparsely scattered swelling may persist for about 5 to 24 over posterior and lateral margins and hours and is quite painful at first. plane surfaces of the abdominal plates. CARAPACE: Color dependent on species. The third, fourth, fifth, and sixth segments Six lateral and two median eyes. The of the female bear a few large granules on lateral eyes are not arranged in a straight the posterior lateral margins of the ab- row. Posterior and dorsal to the two dominal plates. On the male these seg- anterior eyes of each set of three is a raised ments are well covered with granules portion, the lateral superciliary ridges. laterally except the sixth, which is quite Median ocular tubercle quite prominent, densely covered. On both sexes these with fairly well-developed median super- plates are quite smooth except for the ciliary ridges. The ocular tubercle is only extreme posterior edges. The seventh slightly anterior to the midpoint of the segment has a few large granules in the intercarinal spaces. The median keels of 1 Director Poisonous Animals Research Laboratory, Arizona State College, Tempe, Arizona. the seventh segment are very poorly de- 2 AMERICAN MUSEUM NOVITATES [No. 1298 veloped, while the lateral keels consist of keel incomplete on all segments except the a few large granules. Stigma elongate. first, where it is distinctly granulated; Sternum subpentagonal, about twice as marked by moderately large granules on broad as long, with a deep, T-shaped, distal half of segments 2 to 4; and by large median, pit-like furrow. One large bristle granules on proximal half of segment 5. and two or three smaller ones on each half. Superior lateral keels poorly developed but Genital operculum divided medially in both well marked by prominent granules. sexes. Genital papilla not present on male. Dorsal keels are poorly developed but well Four to six large bristles on the posterior marked by moderate-sized granules on the portion of each lateral half. The basal first to fourth; lacking on the fifth. Inter- piece of the pectines broader than long with carinal spaces on superior surface of first a deep, narrow, median furrow extending segment well covered with moderately posteriorly about one-third the length, large granules. Heavy granules also found well covered with large bristles. Three on ventral and lateral faces of segment 5. elongate anterior lamellae, quite well Other segments smooth except the dorso- covered with bristles. About 16 middle lateral areas of segments 2 to 4, which are lamellae, but number is variable. Sub- lightly studded. Telson well covered with circular except first, which is large and long bristles; ampulla subglobate. Ventral somewhat triangular. Each lamellae bears surface moderately studded with low, two to three large bristles. Fulcra sub- broad granules except at the base where triangular and each bearing as many as a few large, denticulate, red granules are five bristles. Teeth, 25-40, more numer- located. The aculeus is black at the distal ous and longer on male than on female, half to two-thirds, and the venom orifices very noticeably so on spadix and arizonen- are a very short distance from the tip in a sis. On the female the distance from the dorsolateral position. These apertures are medial point of attachment of the pectines of a somewhat tear-drop shape with the to the base of the first tooth is much greater globate portion directed proximad, and than the widest portion across both an- receive the venom duct. No subacular terior and middle lamellae. On the male tooth or tubercle. this distance is about the same or less APPENDAGES: Legs light to straw than the combined width of the two yellow color with lateral red spots at joints lamellae. This sexual difference can be between tarsus and protarsus, between detected with the naked eye and is even metatarsus and tibia, and between tibia present on very young specimens. It is and femur. All legs well supplied with the only reliable and distinct external large reddish bristles. Femurs of first characteristic for the sexual differentiation pair of legs one-half as long as those of of H. hirsutus. fourth pair; those of legs 1 to 4 have on CAUDA: Color light to straw yellow their inferior face a double longitudinal with black aculeus. Granules of keels vary series of dentiform granulations, which are from slightly darker yellow to red in color. more distinct on legs 2 and 3 and incom- Segments 1 and 2 lightly bristled but seg- plete and weak on 1 and 4. H. aztecus ments 4 and 5 and ampulla densely bristled. and H. spadix show a greater development Nearly all keels granular and well de- of these granule rows. Claws, unguicular veloped. Inferior median keels all well spines, and pedal spurs well developed. developed; smooth on segments 1 and 2; Pedal spurs bear denticulate spines. The granulated on distal end of segment 3; unguicular lobe is well developed, but no entirely granulated on segment 4; and tarsal spurs are present. The tarsi and strongly denticulate on segment 5. Inferior protarsi bear rows of spines. Fingers of lateral keels well developed; smooth on pedipalps basically light to straw color; segment 1; granulated at extreme distal tipped with red in some species. The end on segments 2 and 3; somewhat cutting edge of the movable finger bears denticulate on segment 4; and strongly nine oblique rows of denticulate granules; denticulate on segment 5. Median lateral the most proximal granule of all but the SCORPIONS OF THE GENUS HADRURUS 3 first row is much larger. The fixed finger veloped median keel bearing a few large bears only seven of these large proximal granules. The outer surface is smooth. granules. Flanking these oblique rows on The inferior, inner border of the movable their inner side is a row of nine large, finger of the chelicera bears a large, black- widely spaced dentiform granules on the tipped tooth and a row of bristles extending movable finger but there are only seven nearly the proximal half of its length. on the fixed digit. Each finger bears on HABITS, HABITATS, AND FOOD: The its extreme distal point a large, somewhat members of this genus are burrowing curved dentiform granule. Hands of the scorpions. They frequently dig down 2 pedipalps moderately bristled. Except for and 3 feet in sandy washes and river banks. a few smooth patches, the superior surface Here they remain, even though the burrow is covered with small granules interspersed has collapsed, apparently finding no with larger ones. The superior digital keel difficulty in breathing. A well-fed Had- is poorly developed except on the finger. rurus may remain thus buried for four The inner superior keel is more pronounced and five months. In experiments, well-fed and covered with large granules at its specimens have been kept in an empty, proximal end, as is also the inner marginal open fruit jar for nine months without food keel. The exterior marginal keel is densely and water. Specimens taken in the field granulated with large, rounded granules. are generally found under boards, sacks of The inner edges of the superior and in- grain, and rocks; or any place that affords ferior surfaces of the brachium are sharp them a cool, dark shelter after a night of and bear large, more or less rounded, prowling.