Comparative studies on the seasonal occurrence, nymphal development and food menu in two giant water bugs,Diplonychus japonicus vuillefroy andDiplonychus major esaki (Hemiptera: Belostomatidae)
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We compared the seasonal changes in population density and nymphal development at different water temperatures and under different food conditions between two giant water bugs,Diplonychus japonicus andD. major, in Okayama, Japan.
D. japonicus produced 1–2 generations a year, whileD. major was strictly inivoltine. The developmental velocity was higher inD. japonicus than inD. major. The thermal constant ofD. japonicus was less than that ofD. major. These results suggest thatD. japonicus is adapted, to higher water temperature thanD. major. In the field,D. japonicus preyed predominately on Lymnaeidae and Physidae snails, whileD. major preyed on aquatic insects such as dragonfly nymphs.
Keywordsexclusive distribution giant water bug Diplonychus japonicus D. major water temperature prey items
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