Variation of the Spermatheca Structure in Two Species of the Genus Palomena Mulsant et Rey, 1866 (Heteroptera, Pentatomidae)

Abstract

Variation in the spermathecal bulb morphology was studied in two species of the genus Palomena Mulsant et Rey, 1866: P. prasina (Linnaeus, 1761) and P. viridissima (Poda, 1761). The spermathecal bulb bears 2–4 processes of different shape and length and is highly variable in both species. The bulb with 2 processes predominates in P. viridissima (75% of specimens examined) while the bulb with 3 processes is marginally more common in P. prasina (56% of specimens examined). The processes are mostly straight in the former species and often curved in different ways in the latter species. The highest variation of the spermathecal bulb in P. viridissima was observed in Primorskii Territory, i.e., the easternmost part of the species range, and in P. prasina, in European Russia and Central Asia. Up to three different types of the spermathecal bulb were found in specimens from one collection locality. Geographic variation of this character was assessed using rarefaction curves to eliminate dependence on the sample size. In some cases, differences in the spermathecal bulb structure were greater between certain geographic populations of the same species than between the two species. Principal component analysis showed that despite the above trends, the two Palomena species did not differ significantly in the spermatheca structure. Therefore, the use of this character for taxa identification requires caution, particularly when conclusions are based on examination of one or a few preparations.