ENTOMOLOGIA HELLENICA 19 (2010): 90-98 *Corresponding author, e-mail: coccidae@mail2000.com.tw Species richness and host-plant diversity are positively correlated in Coccidae Y.-P. LIN 1* , P.J. GULLAN 2 AND L.G. COOK 1 1 The University of Queensland, School of Biological Sciences, Brisbane, QLD, 4072, Australia 2 Department of Entomology, University of California, Davis, CA, U.S.A. ABSTRACT The interactions between insect herbivores and their hosts are among the most fundamental biological associations. Although there are many data available on the host associations of scale insects, there have been few attempts to synthesize the available information. Here we examine host associations of Coccidae, the third most species-rich family of scale insects. We compare host-plant data for most species of coccids that were available from online databases, especially ScaleNet, and the literature, with species richness estimates for host-plant families. Similar to most insect groups, coccids showed high host specialization with about 64% of species recorded from only a single plant family. Analysis of the relationship between species richness of host-plant families and the number of species of coccids recorded on these plants showed a significant positive correlation between host-plant species richness per angiosperm plant family and coccid species richness (P < 0.0001). This is expected under a null model in which host use is randomly distributed across families according to plant species richness of the families. However, the presence of several exceptions (Orchidaceae and Asteraceae in particular) warns that host associations in coccids might be more complex than the correlation analysis suggests. KEYWORDS: host specialization, insect-plant interactions, scale insects, soft scales. Introduction Plants and insects are species-rich and abundant, representing a large proportion of the world’s biodiversity. There is little doubt that herbivorous insects play an important role in plant evolution (Strauss and Zangerl 2002), and these interactions are likely to be reciprocal (Ehrlich and Raven 1964, Winkler and Mitter 2008). Therefore, understanding the relationships between insect herbivores and their hosts is crucial for understanding the evolution of biodiversity. There is a high degree of host specializa- tion in insects (e.g. Wilcox 1979, Janzen 1988, Strauss and Zangerl 2002), with esti- mates of about 80% of herbivorous insects being restricted to a single host-plant family (Schoonhoven et al. 2005). However, there appears to be considerable variation in host- specificity among insect groups (e.g. No- votny et al. 2002). Although the host asso- ciations of many insect groups have been studied (Wilcox 1979, Crawley 1985, Janzen 1988, Bernays and Graham 1988), scale insects (Hemiptera: Sternorrhyncha: Coccoidea) have not yet received much attention. Coc- coids are herbivorous and the superfamily is the most diverse in Sternorrhyncha (Gullan and Martin 2009), with nearly 8,000 de- scribed species (Ben-Dov et al. 2009). The family Coccidae, or “soft scales” or “coc-