MASTOPHORA~~~~JAND WILLIS J. GERTSCH BULLETIN- OF THE AMERICAN MUSEUM OF NATURAL HISTORY ~ .-VOLUME 106: ARTICLE 4 NWYR:15NE'W YORK : 195 5 THE NORTH AMERICAN BOLAS SPIDERS OF THE GENERA MASTOPHORA AND AGATOSTICHUS THE NORTH AMERICAN BOLAS SPIDERS OF THE GENERA MASTOPHORA AND AGATOSTICHUS WILLIS J. GERTSCH Curator, Department of Insects and Spiders BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 106: ARTICLE 4 NEW YORK: 1955 BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY Volume 106, article 4, pages 221-254, text figures 1-48, plates 3-6, table 1 Issued June 6, 1955 Price: 75 cents a copy INTRODUCTION THE SPIDER TRIBE Mastophoreae of the family me, to other American arachnologists, and to Argiopidae comprises a rather small group of spider students all over the world. Even spiders which are notable for their curiously Dr. Nathan Banks, who identified Hutchin- formed and sculptured bodies, for the son's species and made mention of its precocious development and small size of capturing technique in a paper on California the males, and especially for the unique spiders, had completely forgotten the matter method they employ to ensnare flying insects. when I discussed it with him. A generation The ancestors of the group, undoubtedly literally had forgotten Hutchinson's work, stemming from stock using the conventional and it received no notice in the Zoological orbweb, seemingly gained access to all the Record. Therefore, it is particularly grati- principal land areas and attained wide distri- fying for me to acknowledge this classic bution in tropical and subtropical areas of work by Mr. Charles E. Hutchinson and the the world. No species are known from tem- much useful information he gave to me in perate Eurasia or North Africa. The six recent correspondence. known genera still show only modest diver- I also take this opportunity to express my gence from one another in important morpho- gratitude for loans and gifts of material from logical features and close correspondence in the following individuals and institutions: habits and peculiarities. Representative gen- Dr. Edwin Chapin, formerly of the United era now occur principally in three centers, States National Museum, Washington, D. C.; two in tropical and southern Africa, two in the late Miss E. B. Bryant and Dr. Philip J. Oriental Asia from India and Malaya south- Darlington, Jr., of the Museum of Compar- ward through the East Indies into New ative Zo6logy, Cambridge, Massachusetts; Guinea and Australia, and two in the Dr. Henry Dietrich of Cornell University, Americas. The American genus Mastophora Ithaca, New York; Dr. B. J. Kaston of the has an exceptionally wide distribution, Connecticut State Teachers College, New pressing far northward into the temperate Britain, Connecticut; Dr. M. H. Muma of zone to New Hampshire and Minnesota and the Florida State Experiment Station, Lake extending southward through tropical Amer- Alfred, Florida; Dr. H. K. Wallace of the ica into southern Chile. The second American University of Florida, Gainesville, Florida; genus, Agatostichus, has a wide but discon- Dr. H. E. Frizzell of Rolla, Missouri; Dr. tinuous distribution; one species occurs in Allan F. Archer of Union University, Jackson, the state of Baia, Brazil, the other in the Tennessee; and Mr. Walker Van Riper of the lower Rio Grande Valley of Texas, and each Denver Museum, Denver, Colorado. is known from a single adult female. The illustrations used in this paper repre- The present paper is largely concerned with sent the work of several individuals to whom the North and Central American representa- I proffer my sincere thanks. The project was tives of the Mastophoreae. A brief compara- begun several years ago by the late Mrs. tive resum6 brings up to date our knowledge Alma Froederstrom who prepared dorsal of the biology and natural history of these and frontal views of the species then available extraordinary spiders. This is followed by a in the American Museum collection. At about systematic section based on a study of all the same time the figures of Agatostichus material available to me from museums in leucabulba and various epigynal drawings the United States and from personal collec- were prepared by Mr. Wilton Ivie. Miss tions of individuals. A very substantial Alice Gray painted the several illustrations percentage of the total accumulation of of the egg sacs from specimens in the Ameri- material is to be found in the American can Museum collection. The three photo- Museum of Natural History, where the graphs of Mastophora bisaccata were gener- types of the six new species are deposited. ously furnished to me by Mr. M. W. Tyler My especial interest in this group dates of Umatilla, Florida. Finally, it remained from 1946 when Mr. Charles E. Hutchinson for Miss Marjorie Statham to complete the of Glendale, California, brought to my project with the addition of numerous new attention his pioneer work on the biology of drawings and the mounting of the whole Mastophora cornigera Hentz. His careful series for reproduction. study of 1903 was completely unknown to 225 BIOLOGICAL MISCELLANEA THE MASTOPHORIDS substitute an extraor- spinning organ to the length of about two dinary snaring technique for the conven- inches. The thread naturally falls below the tional aerial orbweb trap of their relatives. others, the spider taking care that it shall Hanging fron a horizontal trapeze line, they remain free from entanglement. pull out a short thread from their spinnerets, "The spider with its newly drawn thread weight the end with a globule of viscid still attached now exudes a very small silk, and then hurl it at insects that fly quantity of viscid matter upon the thread at within reach. The picture of a mastophorid its juncture with the spinnerets. No other (pl. 3) with its fishing line held in casting part of this thread bears any viscid matter position is a most dramatic one. Even more nor is any subsequently added. amazing is the series of exacting actions "Pressing the tips of its hind legs firmly necessary to the fashioning of this ingenious upon the thread it pushes each leg backward, tool. The fishing line is drawn out, and we alternately, allowing the thread to slip watch the spider press out viscid droplets between the short, stiff hairs which clothe from the spinnerets and sweep them forward them. With each extension a small quantity with the combs on the hind legs until there of viscid matter is pushed outward and away is built up a shining bola. Meticulous care is from the abdomen as far as the leg will reach. evident in every step from the stringing of At the end of about twenty seconds, during the trapeze lines to the snipping of the line which time each leg is extended eight or ten below the bola and the assumption of the times, there results a globule averaging casting stance. At intervals the line and about 3-32 inch in diameter. globule are rolled up, eaten, and then re- "This finished, the spider undertakes to placed by a fresh line. release itself by severing the line between Nothing was known about the casting its body and the globule. Obviously to technique of the mastophorids until 1903 release the ball suddenly, fastened as it is to a when Charles E. Hutchinson of Glendale, nearly horizontal line, would be to allow an California, published an article entitled oscillation which might readily result in "A bolas-throwing spider" in the Scientific some sort of entanglement and the conse- American. Inasmuch as this vivid description quent destruction of the pendulum. To guard of the habits of the "bolas spider" is largely against such an occurrence the spider first unavailable to spider students, a substantial lengthens the line by playing it out hand over portion of the article is reproduced below: hand, as it were, precisely as a human might "At night-fall the spider (Mastophora perform a like operation, save that legs cornigera Hentz) crawls out to one of the were used in the place of arms, the foot being outermost branchlets and there engages in a well fitted to grasp and hold a thread. most wonderful operation. "The ball having been carefully lowered "The branchlet selected is always one that until its supporting line hangs vertically, or retains a clear space of at least two or three nearly so, the thread running to the spider inches below it when depressed by the is severed by a dexterous movement of the spider's weight. A few short threads are clawed foot, the free end losing itself in the first placed irregularly about the extreme tip globule. As soon as the thread is cut the of the branchlet and along its under side for spider turns about and approaching the pen- a distance of several inches, while additional dulum thread seizes it from above with its threads are carried out to adjacent branches legs. In this act the performer hangs by two to lend stability to the part. or more of the legs of one side to the horizon- "The spider now hangs back downward tally inclined thread to which the pendulum by its legs to the lower threads stretched thread is attached. along the under side of the branchlet. "Reaching well down with one of its long, Attaching a new thread to one of the others arm-like fore legs it grasps the pendulum near one end, it crawls along the horizontally thread between the claws with which the inclined threads below the branchlet, drawing leg is tipped, about half an inch above the out the new thread the while from its ball. By a few well directed movements of 226 1955 GERTSCH: BOLAS SPIDERS 227 the other limbs the upper part of the thread and sinks its fangs into a vital part.