XX…………………………………… ARTÍCULO: Are web stabilimenta attractive to praying mantids? André Walter Abstract: Certain species of orb-weavers add extra silk structures, termed a stabilimen- tum or web decoration, to their webs. In the genus Argiope stabilimenta are ARTÍCULO: silken structures of densely woven zig-zag ribbons. The adaptive value of these stabilimenta is still unclear and controversially discussed. In the course Are web stabilimenta attractive to of time, many functional hypotheses have been proposed for silk stabilimenta. praying mantids? Because of their high visibility they are claimed to act as a visual signal for insects. So most recent hypotheses consider them as prey attractants although André Walter also predators (e.g. mantids) have been shown to be attracted by these struc- tures. Bruce et al. (2001) reported that the praying mantid Archimantis latistylus was attracted to decorated webs of Argiope keyserlingi in a Y-maze choice Institut für Biologie, Bereich Zoologie, test. In Argiope-species spiders construct different basic shapes of stabilimenta Martin-Luther-Universität which can be cruciate, linear or discoid. The predator attraction hypothesis was Halle-Wittenberg, supported by testing cruciate forms of A. keyserlingi. To test these predictions Hoher Weg 4, D-06099 also for linearly shaped stabilimenta, the web decorations of the palearctic Halle (Saale), wasp spider A. bruennichi were tested in a laboratory experiment, adopting the Germany. Y-maze setup of Bruce et al. (2001) to make it comparable. Also a taxonomi- e-mail: [email protected] cally similar predator was used for the test, Mantis religiosa (Mantodea: Manti- halle.de dae). M. religiosa showed no preference for webs with stabilimenta, but only a very small number of individuals reached one of the both maze exits at all, rendering universally valid conclusions difficult. Generally, Mantis showed a scarce locomotor activity in the Y-maze apparatus and no signs of any preda- tory response, which indicates that the experimental design might be problem- atic for studying behavioural elements of praying mantids. Revista Ibérica de Aracnología Keywords: Argiope, stabilimenta, web decorations, praying mantid, Y-maze, choice ISSN: 1576 - 9518. test. Dep. Legal: Z-2656-2000. Vol. 15, 30-VI-2007 Sección: Artículos y Notas. ¿Son los stabilimenta atractivos para los mántidos? Pp: 55 − 61. Fecha publicación: 30 Abril 2008 Resumen: Algunas especies de arañas constructoras de telas orbiculares añaden a sus Edita: telas ciertas estructuras de seda denominadas stabilimentum o decoraciones Grupo Ibérico de Aracnología (GIA) de la tela. En el género Argiope, los stabilimenta son estructuras de seda Grupo de trabajo en Aracnología formadas por cintas en zig-zag densamente entretejidas. El valor adaptativo de la Sociedad Entomológica de estas estructuras no está claro y es objeto de discusión. A lo largo del tiempo Aragonesa (SEA) se han propuesto varias hipótesis sobre la función de los stabilimenta. Debido Avda. Radio Juventud, 37 a su gran visibilidad se ha afirmado que actúan como señales visuales para 50012 Zaragoza (ESPAÑA) los insectos. Por ello, la mayor parte de las hipótesis más recientes, las consi- Tef. 976 324415 deran como atrayentes de presas aunque también se ha demostrado que los Fax. 976 535697 depredadores (por ej. mántidos) pueden ser atraídos por estas estructuras. En C-elect.: [email protected] una prueba de elección en un laberinto en Y, Bruce et al. (2001) encontraron que el mántido Archimantis latislylus era atraído por las telas decoradas de Director: Carles Ribera Argiope keyserlingi. En las especies de Argiope, las arañas construyen dife- C-elect.: [email protected] rentes tipos básicos de stabilimenta, que pueden ser cruzados, lineales o discoidales. Se encontró apoyo para la hipótesis de la atracción probando Indice, resúmenes, abstracts formas cruzadas de A. Keiserlingi. Con el fin de comprobar estas predic- vols. publicados: ciones para los stabilimenta de forma lineal, probamos las decoraciones de las http://entomologia.rediris.es/sea/ telas de la araña avispa paleártica A. bruennichi en un experimento de labora- publicaciones/ria/index.htm torio. Para hacerlo comparable se adoptó el procedimiento del laberinto en Y de Bruce et al (2001). Para la prueba también utilizamos un depredador taxo- Página web GIA: nómicamente similar: Mantis religiosa (Mantodea: Mantidae). M. religiosa no http://entomologia.rediris.es/gia mostró ninguna preferencia por telas con stabilimenta, tan solo solo un peque- ño número de animales alcanzó alguna de las salidas del laberinto, lo que Página web SEA: dificulta obtener conclusiones universales. En general, Mantis mostró una http://entomologia.rediris.es/sea escasa actividad locomotora en el laberinto en Y y ningún signo de respuesta depredadora, lo que indica que el diseño experimental podría resultar proble- mático para estudiar elementos del comportamiento en mántidos. Palabras clave: Argiope, stabilimenta, decoraciones de la tela, Mantis religiosa, laberinto en Y, test de elección. 56 André Walter Introduction 2005). This hypothesis is controversially discussed because there is evidence for the existence of a signal Several araneid, uloborid and nephilid spiders conflict. Bruce et al. (2001) state the conflict of attract- add specific silk decorations so-called stabilimenta ing prey and predators alike. (Simon, 1895) to their webs (Hingston, 1927; Robinson Several personal observations and anecdotal & Robinson, 1973; Scharff & Coddington, 1997; Black- statements report mantids preying upon spiders. This is ledge,1998a). Stabilimenta can differ in shape from in line with the intraguild predation model (see Holt & taxon to taxon (Eberhard, 2003; Bruce & Herberstein, Polis, 1997), according to which spiders cannot be ex- 2005). In the genus Argiope (Araneidae) they consist of cluded from mantids prey spectrum and vice versa. densely woven zig-zag ribbons (Wiehle, 1927; Robinson Since mantids prey recognition depends largely on prey & Robinson, 1973) built of numerous flimsy strands of movements (Reitze & Nentwig, 1991), “[…] the most aciniform silk (Peters, 1993). These structures can vary important interaction between mantids and other mem- largely in shape and size among Argiope-species, popu- bers of the broader generalist predator guild […] may be lations within species, but also among individuals within with cursorial spiders [vagrant web-spinners, crab spi- the same population (Herberstein et al., 2000; Starks, ders, wolf spiders]” (Hurd, 1999; see also Hurd & 2002; Herberstein & Bruce, 2005; Bruce, 2006). Sta- Eisenberg, 1990; Moran & Hurd, 1994). bilimentum building may be temporarily reduced or However, Bruce et al. (2001) observed three even ceased as observed in both field and laboratory predatory strikes of Archimantis latistylus (Mantidae) to studies (Robinson & Robinson, 1974; Lubin, 1975; the cruciate stabilimentum building orb-web spider Nentwig & Heimer, 1987; Seah & Li, 2002; Prokop & Argiope keyserlingi in the field. Inspired from these Grygláková, 2005). Several, partly species-specific, anecdotal events, they tested if silky web decorations stabilimentum types have been classified: e.g. linear, could have functioned as visual cues which attract pray- cruciate or irregular arranged silk bands between adja- ing mantids. In a Y-maze choice test the authors found cent radii, discoid lines, or combined forms of hub- that, when the mantid was confronted with decorated vs. covering silk sheets and silken bands (Wiehle, 1927; non-decorated orb webs of A. keyserlingi, they preferred Nentwig & Heimer, 1987; Herberstein & Bruce, 2005; the decorated web. Consequently, Bruce et al. (2001) Bruce, 2006). suggested that Argiope has to manage a trade-off be- The genus Argiope has become a model group in tween the enhancement of foraging success and the risk terms of testing hypotheses for possible functions of of being preyed by mantids. Yet, only little has been stabilimentum building behaviour (e.g. Edmunds, 1986; published about vision-guided predation upon web- Craig, 1991; Kerr, 1993; Tso, 1996, 1998, 1999, 2004; building spiders (Foelix, 1996; Wise, 1993). So Bruce et Blackledge, 1998a, b; Blackledge & Wenzel, 1999, al. (2001) emphatically demanded comparative data for 2001; Herberstein, 2000; Craig et al., 2001; Seah & Li, their result. 2001; Bruce et al., 2001, 2005; Li & Lee, 2004; Bruce & Here I test the supposed attractive function of Herberstein, 2005). Yet, in spite of the rapidly growing stabilimenta in a comparable European intraguild sys- literature on the stabilimentum phenomenon, the possi- tem, using the common European mantid, Mantis re- ble adaptive functions of these “web-decorations” re- ligiosa Linnaeus (1758) (Mantodea, Mantidae) and the main unclear (see Herberstein et al., 2000; Bruce, 2006; wasp spider Argiope bruennichi (Scopoli, 1772), a see also Robinson & Robinson, 1970). Initially thought common araneid spider with linear stabilimenta. For that to be strengthening or stabilising web structures (hence purpose I adopted the experimental setup of Bruce et al. called “stabilimenta” by Simon, 1895), a fair number of (2001) to ensure methodological comparability. hypotheses have been proposed over the course of time to explain the ambiguous decoration phenomenon (re- Material and methods views in Herberstein et al., 2000; Bruce, 2006). Some STUDY ANIMALS AND REARING argue that stabilimenta act as camouflage devices to hide M. religiosa is an up to 70 mm