Oviposition sites and the number of larval instars of two mountain blackfiy speeies , Simuliztm 1 ` aponiczem and S . Tufcbasis ( Diptera : Simuliidae

.. .......-.. Tm.trAbstract: Oviposition sites and the number of larval instars of two mountain blackfly species, Simulium 1-aponicum Matsumura and S. rufibasis Brunetti, were investigated. Zrhe eggs of both species, which were indistinguishable from each other by egg size, coexisted on bryophytes growing on a water-splashed boulder. They were laid individually without making egg masses, and mest of them were found lower than 5 cm above water level. Two eggs of S. jaPonicum were also found on a partially submerged fal]en leaf. Nine ]arval instars were identified in both species based on the measurements of head capsules of laboratory-reared individuals. The growth rates calculated from the size of head capsules between successive two instars were alrnost constant, i.e., a mean of 1.27± O.082 (S.D.) and 1.25± O.045 for S. japonicum and S. rufibasis, respectively. The oviposition habit of these species was discussed in relation to the habitat conditions.