71 Immatures of Nesticodes ruipes (Araneae, heridiidae) Causing Considerable Damage to Ant Colonies in the Laboratory by Eduardo Gonçalves Paterson Fox1, Antonio Domingos Brescovit2, Daniel Russ Solis1, Carlos Massuretti de Jesus1 & Odair Correa Bueno1 ABStRACt Here we report the frequent occurrence of Nesticodes ruipes (Lucas) (Araneae; heridiidae) immature spiders inside laboratory colonies of various ant species. It was the only spider species frequently found to invade the ant colonies in our laboratory. he spiders were capable of killing ant workers of diferent sizes and were even able to kill queens, and were not always easy to spot. his occurrence adds to the body of knowledge about this species, and may be useful to others trying to rear ant colonies in the laboratory. Key words: spiders, ants, insect rearing IntRODuCtIOn Ants are among the most diverse organisms on the planet and some species are considered important pests that threaten human activities and welfare (Hölldobler & Wilson 1990; Schultz 2000). In order to properly study the biology of ants and colony development parameters, it is frequently necessary to rear these insects in the laboratory. his may prove tricky since various complications, like infestations by parasites and predators, can occur. he theridiid spider Nesticodes ruipes Lucas is one of the most common pantropical spiders which can be found in caves as well as in urban buildings (Levi 1967; Downes 1988; Pinto-da-Rocha 1995). Some studies about its developmental biology have been carried out (e.g. Downes 1988; Gonzáles & Estévez 1988), however, little is known about its general biology. Its role in preying on insects of medical importance has been reported earlier (Bar1 Centro de Estudos de Insectos Sociais, unESP., 24A Av. 1515 - Bela Vista CEP 13506-900 - Rio Claro, SP - Brazil 2 Instituto Butantan Vital Brasil Av. 1500 - Butantã CEP 05503-900 - São Paulo, SP - Brazil 72 Sociobiology Vol. 53, no. 1, 2009 reto et al. 1987; Fox 1998; Rossi et al. 2006; Cushing & Lebeck 1994) and thus it possibly could be one of the most important predators of household arthropods. his study reports the frequent occurrence of immatures of N. ruipes attacking ant colonies reared in the laboratory. It was the only spider species found to invade ant colonies in our laboratory, causing considerable losses. We know of no other records of spiders infesting ant colonies in the laboratory. MAtERIAL AnD MEtHODS Our laboratory is located in São Paulo State university unESP, Rio Claro, SP, Brazil. We keep the core of the colonies inside 10x15 cm2 wooden boxes and glass test tubes of various sizes, which are placed inside 40x55x10 cm plastic trays rimmed with telontM paint and talc to keep the ants from escaping. he ants are mainly fed with insect larvae (Tenebrio spp.) and sugar solution. he plastic trays are kept arranged on steel shelves (Fig. 1), which are held in a room with controlled temperature/humidity conditions of 25±2 Co and 60±10%, respectively, under no ixed light control. he spiders were found by chance during routine maintenance procedures. Voucher specimens of immatures and adults of all cited spider species are deposited in the Arachnida collection of Instituto Butantan of São Paulo, Brazil (responsible curator: Dr. A.D. Brescovit) RESuLtS Small spiders of about 1-2 mm are frequently found at a rate of 1-2 per colony in delicate disorganised webs of variable sizes, always placed over some corner of the ant colonies (Fig. 1). his happened on several occasions (n=52) during the last 5 years in our laboratory. Ant cadavers were always observed scattered on the ground under the web. On ive occasions, spiders were found inside the test tubes and wooden boxes containing the core of the colony (queens and brood). he occurrence of spiders increases when colonies do not contain many workers, due to age or colony stress. he spiders were found infesting laboratory colonies of Solenopsis geminata Fabricius, S. saevissima Smith, S. richteri Forel, S. invicta Buren, Monomorium pharaonis L., M. loricola Jerdon, Linepithema humile Mayr, Camponotus Fox, E.G.P. et al. — Immature Spiders Causing Damage to Laboratory Ant Colonies 73 ruipes Fabricius, C. vittatus Forel, Tapinoma melanocephalum Fabricius, and Paratrechina longicornis Latreille. It should be noted that on one occasion we observed the capture of a major worker of C. ruipes – a 2 cm-long aggressive ant – and it was efectively killed by the small N. ruipes. Spiders were also observed killing queens of S. geminata, P. longicornis, and L. humile (one observation each), causing Fig. 1. Immature of Nesticodes ruipes on a web inside an ant colony of Monomorium loricola. his colony is not held in plastic trays, but directly on the steel shelf. 74 Sociobiology Vol. 53, no. 1, 2009 Fig. 2. Plastic trays arranged in steel shelves containing the ant colonies (displaying Camponotus vittatus). Arrow: location of where adults of Nesticodes ruipes can be found. Fox, E.G.P. et al. — Immature Spiders Causing Damage to Laboratory Ant Colonies 75 the loss of the colonies. no spiders were ever observed feeding on the beetle larvae that are used in feeding the ants. All spiders found inside the ant colonies were identiied as immature forms from both sexes of N. ruipes. Adults, many of which were carrying silky egg sacs, were found only under the lower steel shelves (Fig. 2). Judging from the scattered cadavers, adults were feeding on mosquitoes and escaping ants, chiely C. vittatus. Other spiders occasionally found in this room were Physocyclus globosus taczanowski (Araneae: Pholcidae) (n=25; in webs under the shelves and wall corners) and occasional roaming Plexippus paykulli Audouin (Araneae: Salticidae) (n=11). none of the above two species were found living inside the ant colonies, however, salticids were twice observed in colony trays. One immature specimen of N. ruipes was manually placed amidst workers of S. invicta and managed to escape by outrunning S. invicta workers and entangling their antennae with silk draglines, and it even autotomised a hind leg that was being bitten by a larger worker – the leg remained irmly attached to the tray loor with the worker still holding it. Another immature spider managed to escape workers of C. vittatus by similar means, while an adult specimen later placed in a ire ant colony tray was promptly captured and killed. Additionally, specimens of the other two spiders found in the room – P. globosus and P. paykulli – were observed being devoured by ants ater having accidentally fallen in rearing trays of P. longicornis and L. humile, suggesting that they are not very eicient in escaping the ants once inside the trays. We think these observations indicate that the immature forms of N. ruipes are the only spiders in this rearing room that are capable of successfully invading and attacking ant colonies on a regular basis. DISCuSSIOn Our observations illustrate that a common household spider can successfully and continuously invade laboratory colonies of diferent ant species, and that they can kill ants of diferent sizes and queens. We do not think such invasions would take place in the ield – because the conditions imposed on the ant colonies are very artiicial – but we do feel it is possible that the immatures of this spider are well-adapted to capturing and escaping ants. 76 Sociobiology Vol. 53, no. 1, 2009 Fox (1998) hypothesized the presence of a paralysing substance on the web of N. ruipes, when observing the capture of mosquitoes. However, Rossi et al. (2006) reported no observed paralysis when studying the capture of Musca domestica by N. ruipes, and hypothesized that the paralysing efects described by Fox (1998) might only take efect on smaller insects. Herein, we would like to report noticing no such efect on ants, as most of them (in 5 out of 8 observations) could free themselves of the web if they struggled hard enough and were not bitten by the spiders. Most ants captured had to be subdued by the poison of the spiders, even small specimens. Nesticodes ruipes immatures were capable of killing workers and even queens of colonies of diferent ant species, regardless of their size or aggressiveness. Some colonies were lost when the active queen was killed and when many workers of a small colony were captured. Researchers rearing ant colonies should therefore be wary of the presence of immature spiders in ant laboratory colonies, and know that they may not be easily spotted (if inside the colony core). he loss of an entire laboratory colony can greatly delay projects and be very expensive. Finally, we hope our observations may add to the knowledge of the behavior and biology of N. ruipes in a laboratory environment, and that this report may stand as a warning to those rearing ants in the laboratory. ACKnOWLEDGMEntS We thank Dr. Gail Stratton, Dr. Johan Billen, and Dr. Birgit C. SchlickSteiner for constructive comments onearlier versions of this manuscript. he irst author was supported bu Fundação de Amparo á Pesquisa do Estado de São Paulo (FAPESP), grant #2006/02115-6. REFEREnCES Barreto, M., P. Barreto & A. D’Alessandro 1987. Predation on Rhodnius prolixus (Hemiptera: Reduviidae) by the spider heridion ruipes (Araneida: heridiidae). J. Med. Entomol. 24:115-116. Cushing, B.S. & L. M. Lebeck 1994. Foraging in cockroach sticky traps by the spider Nesticodes ruipes Lucas (Araneae: heridiidae): a super food resource. Acta Arachnol. 43:49-55. Downes, M.F. 1988. he efect of temperature on oviposition interval and early development in heridion ruipes (Araneae: heridiidae). J. Arachn. 16:41-45. Fox, E.G.P. et al. — Immature Spiders Causing Damage to Laboratory Ant Colonies 77 Fox, I. 1998. Predation on Aedes aegypti (Diptera: Culicidae) by heridion ruipes (Araneae: heridiidae) in Puerto Rico. J. Med. Entomol. 35:611-613. González, A. & A.L. Estévez 1988. 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