Great Basin Naturalist

Volume 52 Number 4 Article 15

12-30-1992

Notes on (, Salticidae) predation of the harvester , salinus Olsen (: Formicidae: ), and a possible parasitoid fly (Chloropidae)

William H. Clark Albertson College of Idaho, Caldwell, and University of Idaho, Moscow

Paul E. Blom University of Idaho, Moscow

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Recommended Citation Clark, William H. and Blom, Paul E. (1992) "Notes on spider (Theridiidae, Salticidae) predation of the harvester ant, Pogonomyrmex salinus Olsen (Hymenoptera: Formicidae: Myrmicinae), and a possible parasitoid fly (Chloropidae)," Great Basin Naturalist: Vol. 52 : No. 4 , Article 15. Available at: https://scholarsarchive.byu.edu/gbn/vol52/iss4/15

This Note is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Creat Busin Naturalist 52(4), pp. 385--386

NOTES ON SPIDER (THERIDIIDAE, SALTICIDAE) PREDATION OF THE HARVESTER ANT, POGONOMYRMEX SALINUS OLSEN (HYMENOPTER.A: FORMICIDAE: MYRMICINAE), A1 DA POSSIBLE PARASITOID FLY (CHLOROPIDAE)

William H. ClarkI and Paul E. BJorn2

Key words: PogOilomynnex salin us, haf"fJester , Eut)'opis formosa, Xysticus, spider predators, Incertellu, pam~ite.

Spiders are known predators of ants. Pres­ that was caIT}ing a worker of Pogonornyrmex sure exerted by consistent spider predation can salinus Olsen (Hymenoptera: Fonnicidae, alter the behavior of ant colonies (MacKay Myrmicinae) across a large area of basalt rock. 1982) and may be a selective pressure contrib­ The ants were actively foraging in the area. The uting to the seed-harvesting behavior of air temperature (shaded) was 31 C and the soil Pogonomyrmex (MacKay and MacKay 1984). surface (in thesun) was 39.5C. Nootherspiders We observed the spider of this species were encountered. Prey capture Banks (Araneae: Theridiidae) capture and was not observed. transport workers of the harvester ant On 31 August 1991 at 1725 h at the Clark (Pogonomyrmex saliDus Olsen [Hymenoptera: County site we observed a crab spider of the Formicidae, MyrmicinaeJ) in southeastem Xystictls preying on P salintls about 20cm Idaho. Additional observations revealed a crab from the ant nest entrance. The ants were still spider of the genus Xysticus preying on P. actively foraging at this time. One spider was saliDus and the presence of a chloropid fly riding on the ant in the shelter of an isolated (Incertella) that may have been parasitizing the clump of Indian ricegrass (Oryzopsis hyme­ moribund prey subdued by the spider. ,wides) at the edge of the ant mound. The ant was initially very active, walking around an old STUDY SITE grass stem, while the spider made periodic attacks on the ant. As time progressed, involun­ One collection site is located along Road tary spasms in the ant increased. The spiderwas T-20 (Butte County, T4N, R31E, S6) on the generally oriented toward the posterior of the Idaho National Environmental Research Park ant, biting it at the base of the petiole. Some­ (lNERP) in the cold deselt of southeastern times the spider was perpendicular to the ant, Idaho. Tbe secondset ofobservations was made holding on to the ant with only its mandibles. on the INERP (Clark County, TIN, R31E, 534, After five minutes the ant fell onto its side and along Highway 28). Voucher specimens of all movements slowed.. At 1740 h only its antennae species have been deposited at the anna J. were moving slightly, and a minute later the Smith Museum of Natural History, Albertson College of Idaho, Caldwell, Idaho 83605 USA spider moved ti,e ant under a small stick. Two (ClDA). small flies approached the ant and oneflew onto its head. Occasional movements Uerks) of the RESULTS AND DISCUSSION ant's legs were observed at 1751 h. At this time we collected the spider, the ant, and one ofthe On 3 July 1988, 1020 h, at the Butte County rues (WHC#9170).The fly is a female Incertella collection site wecollecteda single individual of (Diptera: Chloropidae) and may represent an Euryopisformosa Banks (Arancae: Theridiidae) undescribed species. BrO"'"IJ and Feener (1991)

lOnna J. Smith Museum ofN"lura! HistOl)', Albertson College o:i Idaho, Caldwell. Tdllho83605 lJSA; and Dqrortment ofP1;mI. Soil. lUlll I-:nt;:nnol

385 386 GREAT BASIN NATURALIST [Volume 52

have found the phoridApocephaIuR pamponeme small gray capture ants on their monnds selectivelyparasitizing moribundworkers ofPara­ and drag them away by a web sling attached to ponera clavata. It may be that these Incertella. the ant and to the tip of the spider's abdomen. flies are seeking a similar host and opportunis­ Euryopsis forrrwsa is found from central Cali­ tically exploiting the spider prey. The Hies were fornia north to British Columbia and east to not observed to interact with living, active ants. Wyoming (Levi 1954). E. formosa may also be At 1740 h we noticed a second spider, E. an important predator of P salinus at this site formosa, on the same ant mound. This spider and of Pogonomyrmex species in the western oriented uphill on the side ofthe mouud, facing United States. The relatively greater precision the ant nest entrance. At 1742 h an ant walked and speed with wbich Euryopsis subdned and over and slightly past the spider, apparently transported the P. salin1J.s prey suggests an failing to recognize thepredator's presence. The established predator-prey relationship. spider remained motionless as the ant passed, then spun around and mounted the ant's gaster. ACKNOWLEDGMENTS The spider released the ant and moved to face This work was condncted under the INEL it. The ant beglm convulsing at this time, while Radioecologyand Ecology Programs sponsored the spider sat 1 cm away from the ant (facing by the office of Health and Environmental away from the ant). By 1745 h no motion was Research, and the Division of Waste Products observed in the ant and at 1746 h the spider throngh the Fuel Reprocessing andWaste Man­ climbed onto the ,mt. The ant was on its side agement Division, United States Departmentof with the spider on top facing the gaster. A Hy Energy. O. D. Markham, T. D. Reynolds, and similar to those mentioned above moved onto J. B. Johnson have provided assistance. J. the head of the ant. At 1747 h the spider was McCaffrey and I-I. W. Levi provided spider dragging the ant across the mound using a web determinations. C. W. Sabrosk-y identified the sling, as previously described by POlter and Incertella. specimen and B. V. Brown assisted. Eastmond (1982) for the spiderE. wki in south­ This paper is published as Idaho Agriculture eastern Idaho. The spiderdragged the ant to the Experiment Station Paper No. 91767. edge of the mound and into the grass clump mentioned earlier. Several other worker ants LlTERATUHE CITED were observed strungup in the grass clumps. At this point we collected the spider (WHC #9171). ALLHED, D. M. 1969. Spiders ofthe National Reactor Test~ ing Station. Great Basin Naturalist 29: 105-108. The spider genus Euryopis is known to prey BLOM, P. E., W H. CLAHK, AND J. B. JOHNSON, 1991. on ants (Levi 1954, Carico 1978), including har­ Colony densities of the seed harvesting ant vester ants of the genus Pogonornyrmex in Pogorwmyrmexsalinus (Hymenoptera: Formicidae) in seven plant commnnities on the Idaho National Engi­ (MacKay 1982, Porterand East­ neering Laboratory. Journal of the Idaho Academy of mond 1982). MacKay (1982) has reported Science 27: 2&-36, E. californica preying on P. rugosus in southern BnowN, B. V, AND D. H. F'EENEH, In. 1991. Behavior and California. host location cues ofApocerphalus paraponerae (Dip­ tera: Phoridae), a parasitoid of the giant tropical ant, Prey of E. fomwsa has not previously been Paraponera clavata (Hymenoptera: Formicidae). reported (Levi 1954), nor has the spider been Biotropica 23: 182-187. reported hom the INERP (Levi 1954, Allred CA1UCO, J. K 1978. Predatory beh'!vior in Euryopisfuneris ~ives (Hentz) (Aranea: Theridiidae) and the evolutionary 1969). Levi (1954) the distribution of the significance ofweb reduction, Symposium ofthe Zoo­ species over most ot Idaho except for the south­ logical Society of London 42: 51--58. western conler, so its presence here was ex­ J....nVI. H. W, 1954. Spiders of the genus Euryopsis from pected. Allred (1969) reported a related species, North and Central America. American Museum Novitates 1666: 1-48, Euryopis scriptipes Banks, from the southeastern MACK.W, W, E 1982. The effect of predation of western border of INERP dnring July. Pogonomyrmex widow spiders (Araneae: Theridiidae) on hmvesterants salinus is the dominant seed-hmvesting ant on the (Hymenoptera: Formicidae). Oecologia 53: 406-411. INERp, occuning in almost all ofits plant mmmu­ MAcKAy, W, P.,AND E. E. MACKAY. 1984. Why do harvester ants store seeds in their nests? SOciobiology 9: 31--41, rilties (Blom et aI. 1991). POHTE-n, S. D., AND D. A. EASTMOND, 1982. kuryopis coki Porter mld Eastmond (1982) found Euryop­ (Theridiidae), a ~1)ider that preys on Pogownnyrrnex sis coki Levi to be a common predator of ants, Journal ofArachnology 10: 275--217. Pogonornynnex owyheei (=P. salinus) in south­ Received 6 February 1992 eastern Idaho during July and August. These Accepted 10 SepU-0'I'Jwl" 1992