Life history, growth patterns and feeding habits were compared between two common predatory stream stoneflies, Skwala pusilla and Kamimuria tibialis. Both species are univoltine with the larvae appearing in the streams in summer and showing high growth rates in autumn. Skwala pusilla continued growing to the final instar during winter, and then emerged in early spring. In contrast, the growth of K. tibialis stagnated in winter and turned high again in spring when they molted to the final instar. Skwala pusilla consumed a higher proportion of algae than did K. tibialis, and a randomisation test indicated significant difference between the two species in the degree of carnivory. However, S. pusilla did not enhance the degree of carnivory in winter when the growth of K. tibialis stagnated. These results suggest that the relatively low degree of carnivory in S. pusilla is not due to interspecific competition for prey resources.
Tetraneura nigriabdominalis (Sasaki, 1899) is a galling aphid that is distributed widely in Eurasia. In the present study, a diagnostic multiplex polymerase chain reaction (PCR) protocol was developed to discriminate two types of the cytochrome oxidase subunit I (COI) sequences in this species, and its usefulness was examined from 25 samples of T. nigriabdominalis. Multiplex PCR and electrophoresis revealed that 10 and 15 samples had one band of 133 bp (type A) and 426 bp (type B), respectively. This discrimination was identical to the division of the 25 samples based on the alignments of COI sequences (511 bp), indicating high accuracy of this protocol in distinguishing the two types. This protocol is useful for studying microgeographic distributions of the two types and genetic diversities in T. nigriabdominalis.
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