Cyrtophora

Abstract: Among spiders, some species could be qualified as colonial. Individuals may live alone or in colonies where each spider exploits its own capture web in a communal network. We compared solitary with colonial life in Cyrtophora female populations from South-East Sicily in 1992 and 1993. We used 6 parameters to describe and compare the populations: spider size, web size, egg production, prey captured, presence of kleptoparasites and their size.¶ Spiders living in colonies did not differ in size from solitary spiders.¶ The webs of colonial spiders were smaller than those of solitary spiders.¶ The number of prey captured and their size did not differ between the two types of spiders.¶ Solitary spiders produced more eggs than colonial individuals.¶ Kleptoparasite spiders Argyrodes gibbosus were more numerous in the webs of solitary spiders than in the webs of colonial spiders and there were more solitary webs infested by kleptoparasites in 1992. The kleptoparasites were larger in colonial webs than in solitary ones. Another species of spider, Holocnemus pulchei, spun its own web in the network of the web of Cyrtophora. The number of Holocnemus per web did not differ between solitary and colonial Cyrtophora.¶ Results are discussed by referring to what it is known in other temporarily social spiders.

Abstract: Throughout this book we have seen numerous examples of the flexible nature of spider behaviour. This includes flexibility in silk and web production and design; foraging, anti-predatory and deceptive behaviour; and sociality and courtship behaviour. We have also seen how behavioural plasticity and learning enhances the flexibility of these different behaviours. In this chapter we will look at a subfamily of spiders, Argyrodinae (Theridiidae), to see how all these forms of flexibility contribute to the success of this group. Argyrodinae are by no means the most successful group of spiders, nor are they likely to be the most intelligent (if it were possible to measure such a thing in spiders, that award would undoubtedly go to individuals in the Portia genus) but they are an interesting group of spiders that illustrate many of the concepts discussed in the book, and they also show some unusual takes on common themes. Introduction The subfamily Argyrodinae, which contains over 200 species, is well known for its association with the webs of other spiders, and the range of foraging techniques this group uses to exploit other spiders. For example, there are species that glean insects off the edge of the web (e.g. Henaut, 2000, Kullmann, 1959), eat the silk from the web (e.g. Cangialosi, 1991, Grostal and Walter, 1997, Kerr and Quenga, 2004, Miyashita et al ., 2004), steal food bundles caught and wrapped by the host spider (e.g. Henaut et al ., 2007, Vollrath, 1984, Whitehouse, 1997a), attack the host while it is moulting (Cangialosi, 1990, Tanaka, 1984, Whitehouse, 1986) and actively prey on the host or its young (Eberhard, 1979, Larcher and Wise, 1985, Smith Trail, 1980) by either by throwing a sticky thread (Eberhard, 1979, Whitehouse, 1987a) or by lunging at them (Whitehouse, 1986).

Abstract: Parasitoid wasps of the Polysphincta genus-group are highly specialised on their spider hosts, and most of them are known to manipulate their hosts into building a special web in which the parasitoid pupates. Trophic niche and the plasticity of host use were investigated in the koinobiont parasitoid Zatypota kauros Gauld from Queensland, Australia. We found that Z. kauros attacks spider hosts from different families, each differing widely in their web-building behaviours, which makes it unique in the breadth of its host range. Molecular analyses revealed that the taxon Z. kauros contains three divergent mitochondrial lineages. Lineage A was associated exclusively with spiders of the genus Anelosimus (Theridiidae), which builds tangle webs; lineage B was associated with the genus Cyrtophora (Araneidae), which weaves tent webs; and lineage C was associated with a broad range of hosts, including spiders of both the families Araneidae and Theridiidae. Unique host manipulations could be observed in the web-building behaviours of the different host groups. Nevertheless, nuclear data from two ribosomal genes and three introns did not add any support to the existence of different evolutionary lineages, nor did they coincide with the different host groups. The partial correspondence of mitochondrial lineage and host use, together with an apparent mito-nuclear conflict might indicate maternal effects or very recent and/or incomplete speciation in this taxon. Given their wide host range and intriguing interactions with their hosts, the Z. kauros complex represents a promising system for studying parasitoid specialisation and its potential impact on speciation.

Abstract: The spinning apparatus of Cyrtophora citricola closely corresponds to that of orb-weaving Araneidae, two peculiarities excepted. Firstly the spigots of the piriform glands differ extremely in size, the smallest of them being numerous and having a unique location on the anterior spinnerets. Secondly, the triad complex (on the posterior spinnerets) used by other Araneidae for producing gluey capture threads is lacking. Both these characteristics are correlated with the construction of a fine meshed sheet of dry silk by Cyrtophora instead of orbwebs with capture spirals. The sheet can be understood as being a very much enlarged central area of orb-webs. Since vestiges of triads could be found in early developmental stages of C. citricola, the origin of the meshed sheet from orb-webs with gluey capture threads is clearly demonstrated. The paper includes a study on how the spider produces thread attachments by means of the secretions of the piriform glands.