BEHAVIORAL CHARACTERS FOR THE HIGHER CLASSIFICATION OF ORB‐WEAVING SPIDERS

A number of studies have shown that behavior patterns can be useful taxonomic characters (see review by Mayr, 1958; also Evans, 1966; Crane, 1975; Michener et al., 1978; Eickwort and Sakagami, 1979; Greene, 1979). The webs and web-building behavior of orb-weaving spiders are complex, apparently stereotyped characters, and as such offer promise of being useful in indicating taxonomic affinities. As Levi (1978a, 1978b) has noted, however, this promise has not been fulfilled. The gross, relatively superficial web characters such as the presence or absence of stabilimenta, or open versus closed hubs which have been studied to date have not proved to be useful indicators of subfamilial relations. Webs are directly involved in orb weavers' interactions with a number of aspects of their environments (particularly prey), and relatively minor changes in environmental factors could result in selection for changes in web form. Levi argues (echoing Darwin, 1859) that at least some aspects of web design might thus be expected to be evolutionarily nonconservative and of little use in indicating higher taxonomic relationships. This does not, however, eliminate the possibility that webs and web-building behavior may be useful as taxonomic characters. It is possible that some details of web design with apparently low functional significance may be more conservative than other more obviously functional characters. I have the impression that many web characters are not scattered randomly among the webs of araneoid species, and that their patterns of occurrence will be of at least some use in systematics, particularly at generic and tribal levels. The analysis necessary to substantiate this has yet to be performed, although Risch (1977) has made a promising start by finding that two congeneric species' webs were more similar to each other in a number of details than to those of two species from other genera. It is also possible that some details of construction behavior are employed by spiders in unchanged form to construct a variety of different web forms, and that these behaviors are thus slow to evolve even while the webs themselves change rapidly. This paper describes several such behaviors and shows that they are conservative enough to characterize the classical subfamily and family groupings which have been based on adult morphology and can thus be used to indicate relationships between them, a topic on which there is currently substantial disagreement (e.g., Lehtinen, 1967, 1975; Levi, 1978a, 1980; Robinson and Robinson, 1978, 1980; Opell, 1979). Obviously the more characters used in constructing a system of relationships the greater the likelihood of the results being correct. A great deal is known about the morphology of orb weavers, but no comprehensive surveys of characters are yet available (but see Levi, 1980), so they cannot yet be included. This paper is meant to provide useful data for later syntheses, not to give the final word on the classification of orb weavers.