Arachnologische Mitteilungen 57

Arachnologische Mitteilungen / Arachnology Letters 57: 31-36 Karlsruhe, April 2019 Spiders are primarily known as predators, mainly feeding on small invertebrates. An exception is Bagheera kiplingi Peck- ham & Peckham, 1896 (Salticidae) which largely feeds on plant products (Beltian bodies and foliar nectar) from aca- cias ( Vachellia sp.) (Meehan et al. 2009). Some other spiders ocassionally supplement their diet with plant resources. Nyf- feler et al. (2016) summarised 95 known incidents of spiders feeding on plants; mostly under natural conditions. In their review, plant resources used by spiders were divided into six main groups: 1. leaves (Beltian and Müllerian bodies, plant sap), 2. sugar solutions (floral and extrafloral nectar, honeydew as a plant-derived sugary fluid, stigmatic exudates), 3. pollen, 4. seeds, 5. spores and 6. plant material present in the guts of herbivorous prey. Among these cases, seed feeding by spiders consisted of only two reports. First, an orb-weaving spider, Neoscona adianta (Walckenaer, 1802) (Araneidae), was obser- ved sucking a grass seed (Poaceae) (Berland 1933). Second, it was assumed by Nyffeler et al. (2016) that tiny airborne plant seeds trapped in spider webs become unintentionally ingested along with the old threads during the recycling process. Fur- thermore, raising spiders on a liquid diet made from the seeds of Glycine max (L.) Merr., 1917 (Fabaceae) under laboratory conditions was reported by Amalin et al. (1999, 2001). Due to the above mentioned scarcity of reports of spiders feeding on plants, and especially on seeds, it was a surprise to see (on 5.I.2018) two relatively heavy seeds of Costus dubius (Afzel.) K. Schum. (1904) (Costaceae) in the web of a Pa- rasteatoda (Theridiidae) above the inner sill of a greenhouse window in the Botanical Garden of the P. J. Šafárik University in Košice (hereinafter BG PJŠU). About three weeks before (12.XII.2017), the seeds of C. dubius were intentionally scat- tered here to observe their transport by local ants (especially Lasius sp.). While preparing a study on ants in greenhouses many seeds remained on the window sill. The question was whether some seeds later enetered the spider‘s web randomly or whether this spider actually pulled them up as a food. In the second option, it would be interesting to see whether dia- spores of this type (seeds or fruits with elaiosomes) could also be used by other spiders. Myrmecochory is a phenomenon more or less widespread all over the world, in which diaspores of myrmecochorous plant species are adapted for distribution by ants. Such di- aspores are usually equipped with elaiosomes: appendages of specific composition, rich mainly in proteins and fatty acids. According to Lengyel et al. (2010), the number of myrme- cochorous plant species can be estimated to be at least 11000 in 77 families and according to World Spider Catalog (2018), there are 47904 accepted spider species in 117 families. To date, consumption of such seeds or fruits by spiders has not been reported. Material and methods More than 4000 higher plant taxa are registered in the BG PJŠU (48.735°N, 21.238°E, 220–370 m a.s.l.), about 2500 of them from tropical and subtropical areas growing in heated greenhouses (Mártonfiová et al. 2010). Adaptations for myr­ mecochory are known for about 300 species but in fact dia- spores were disposable only from one tropical species, Costus Diaspores of myrmecochorous plants as food for certain spiders Martin Suvák doi: 10.30963/aramit5706 Abstract. Spiders eating diaspores (seeds and fruits) frommyrmecochorous plants – i.e. those adapted to distribution by ants – is recor- ded here for the first time as a new case of herbivory in these typical predators. Having found seeds of Costus dubius (Afzel.) K. Schum. (1904) trapped in the web of a Parasteatoda spider (Theridiidae), tests with available myrmecochorous seeds and spiders in the green- houses of the Botanical garden of the P. J. Šafárik University in Košice (Slovakia) were carried out. Parasteatoda spiders can actively collect C. dubius seeds near their webs and feed on them for a long time. Diaspores with elaiosomes (nutrient-rich appendages) from five other myrmecochorous plant species thrown directly into webs of Parasteatoda sp. and Uloborus plumipes Lucas, 1846 (Uloboridae), another spider species very abundant at this location, were also consumed. These initial observations show that the special chemical composition of elaiosomes, which imitates insect prey primarily for ants, can be attractive for some spider species too. Considering the tested taxa, in the case of Uloboridae contact with such food sources is improbable in their typical niches. However, at least some Theridiidae could also consume myrmecochorous diaspores in nature, especially if they are near source plants or paths of ants transporting these diaspores. Keywords: Araneae, elaiosomes, herbivory, myrmecochory, Parasteatoda , Uloborus plumipes Zusammenfassung. Diasporen von Pflanzen mit Myrmekochorie als Nahrung für manche Spinnen. Als neuer Fall von Herbivorie durch typischerweise räuberische Spinnen wird erstmals belegt, dass Spinnen Diasporen (Samen und Früchte) von Pflanzen mit Myrme- kochorie (Ameisenausbreitung) fressen. Als Samen von Costus dubius (Afzel.) K. Schum. (1904) im Netz von Parasteatoda -Arten (Theridii- dae) gefunden wurden, wurden Test mit verfügbaren Samen von Pflanzen mit Myrmekochorie und Spinnen in den Gewächshäusern des Botanischen Gartens der P.J. Šafárik Universität in Košice (Slowakei) durchgeführt. Es konnte bestätigt werden, dass Parasteatoda -Arten aktiv Samen von C. dubius in der Nähe iher Netze sammeln und sich davon über längere Zeit ernähren können. Diasporenmit Elaiosomen (energiereiche Anhängsel,„Ölkörperchen“) fünf weiterer Pflanzenarten mit Myrmekochorie, die direkt in die Netze von Parasteatoda sp. und von Uloborus plumipes Lucas, 1846 (Uloboridae) gegeben wurden – letztere Art kam ebenfalls sehr häufig vor, wurden ebenfalls gefressen. Diese ersten Beobachtungen zeigen, dass die besondere chemische Zusammensetzung der Elaiosomen, die primär Insekten- nahrung für Ameisen imitieren, auch attraktiv für manche Spinnenarten sein können. Im Fall der untersuchten Uloboridae ist ein Kontakt mit solcher Nahrung in ihrem typischen Lebensraum unwahrscheinlich. Aber mindestens einige Theridiidae-Arten könnten in ihrem natürlichen Lebensraum Diasporen von Pflanzen mit Myrmekochorie ebenfalls fressen, insbesondere in der Nähe der Pflanzen oder von Ameisenstraßen, wo solche Diasporen transportiert werden. Martin SUVÁK: Botanical Garden of P. J. Šafárik University, Mánesova 23, 043 52 Košice, Slovakia; E-mail: martin.suvak@upjs.sk submitted 17.12.2018, accepted 4.2.2019, online 20.2.2019