Open, B. D. 1984. Comparison of carapace features in the familyUloboridae (Amneae). J. ArachnoL, 12:105-114. COMPARISON OF CARAPACE FEATURES IN THE FAMILY ULOBORIDAE (ARANEAE) Brent D. Opell Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 ABSTRACT Cluster anal.vses of 51 quantified carapace features from eachof 34 species representing all known ulobotid genera fail to produce a consistentpattern of overall similarity. However, a minimum span- ningtree and a principal axis analysis of these features shows that formation of PLE tubercles and other anterior lateral carapace changes are most responsible for explaining carapace diversitywithin the Uloboridae. Many of these same features are shown by discriminant analysis to be most highly correlatedwithweb type, indicatingthat they are functionally linked to changes in web monitoring and use. Asurvey of the enctosternitesof Hyptiores, Miagrammopes, and Philoponella, and carapace musculature of the latter twogenerashows many changes in carapaceform to be associated with muscle reorientation that facilitates use of a reduced orb-web. The presence of eyetubercles associated with the most extremely modified carapaces also appears to ventrally extend the spider’s vision. INTRODUCTION Carapace modification was strongly reflected in early classifications of the family Uloboridae (O. Pickard-Cambridge 1869, Simon1874, 1892, Dahl 1904). The subfamily Uloborinae traditionally contained orb-weavers with a generalized, pear-shaped carapace (Fig. 4); I-Iyptiotinae, triangle-web weaverswith a broad, anteriorly narrowed carapace (Fig. 6); and Miagrammopinae, members with a rectangular carapace that bore only the four posterior eyes (Fig. 8) and were later found to construct reduced webs of only one or a few lines (Akerman 1932, Lubin et al. 1978). The number of uloborid genera has increased from an initial one per subfamily to 22 (Lehtinen 1967, Lubin et al. 1982, Opel] 1979, in press a), 14 of which would fall within the traditional bounds of the Uloborinae. However, shifting emphasis from carapace form and eye arrangement to other characters such as details of male and female genitalia caused Lehtinen (1967) establish the subfamily Tangaroinae, and me (Opell 1979) to conclude that uloborids with a generalized carapace are not monophyletic. The purpose of this study is to quantify and compare carapace features of representa- tives of all known uloborid genera in order to assess the significance of carapace shape within the family. Carapace form may mirror the family’s phylogeny or it may more closely reflect muscle reorientation or other functional changes associated with orb-web modification. These hypotheses do not entirely exclude one another, as the use of re- duced, vertical webs is characteristic of the related genera Poleneda, Hyptiotes, and Miagrammopes (Opell 1979, in press b). However, modified orb-webs are constructed