We found that body length of a minute eriophyoid mite, Abacarus panticis Keifer, increased with elevation and rainfall, decreased with temperature, and exhibited a female‐biased dimorphism. There was a negative temperature–body length relation in the female instead of the male, whose size remained constant along temperature gradients. In addition, scaling of body length between sexes is not significantly different from one. We conclude that within‐species body length of A. panticis conforms to Bergmann's trend but not Rensch's rule. Further studies could take advantage of the more rigorous and flexible hierarchical model in the revelation of scale‐specific determinants of phenotypic variation.

Unambiguous classification is a prerequisite for the study of polymorphism, but accurate delimitation of continuous morphological characters can be challenging. Finite mixture modeling is a rigorous and flexible approach for delimiting continuous variables with unknown prior membership, but its application to morphological studies remains limited. In this study, the lengths of scapular setae of the eriophyoid mite Abacarus panticis Keifer collected from 18 sites in Taiwan were used as an example to evaluate the eligibility of finite mixture models. We then tested the hypothesis that longer scapular setae can facilitate dispersal. Lastly, we investigate morphological variation in various seta morphs by geometric morphometric techniques. Finite mixture models can satisfactorily classify scapular setae of A. panticis into long and short seta morphs. Abacarus panticis of the long morph only occurred in five sites whereas the short seta morph existed in all study sites. Geometric morphometric analyses revealed a more elongated coxal area in individuals of long morph than in those of short morph. Because the short morph is more widespread in geographical distribution than the long morph, longer scapular setae seem unlikely a specialized adaptation for dispersal. Further studies should capitalize on the finite mixture model in the delimitation of continuous morphological characters.

Morphological variation of Huangiella lanyuensis (Huang, 2001) and Tumoris sanasaii Huang, 2001 from Taiwan was analyzed using multivariate statistical methods. We show that these species are the same and propose to use the name Tumoris sanasaii. No significant differences between populations from Lanyu and Green Island (type localities for Huangiella lanyuensis and Tumoris sanasaii, respectively) were found; however, mites from Yangmingshan (northern Taiwan) differed substantially from these two groups. Synonymy resulted from our study is as follows: Huangiella Kammerer, 2006 is a junior synonym of Tumoris Huang, 2001; Absentia lanyuensis Huang, 2001 is a junior synonym of Tumoris sanasaii Huang, 2001. We also study the sexual variation of populations from Green Island. The result showed the females significantly larger than the males at 17 variables.