Distribution and Ecological Characteristics of Cocoons of the Solitary Bees Osmia cornifrons and O. pedicornis (Hymenoptera: Megachilidae)

Osmia cornifrons and O. pedicornis are a cavity-nesting solitary species used mainly as an apple pollinator in Korea. To elucidate the characteristics of those bees for the efficient the pollination of agricultural crops, we investigated the distribution, the number of cocoons per straw, sex ratio, and characteristics of cocoon at different locations in 2010. We collected four species of Osmia spp. consisting of O. cornifrons, O. pedicornis, O. taurus and O. satoi in Yeongwol, Bonghwa and Yechon locations. O. pedicornis was the dominant species, which accounts for 59.6% to 76.4% in the three locations. The mean number of Osmia spp. was varied in different 3 locations. In the number of cocoons per bamboo straw, there were from 7.6 to 8.5 in O. cornifrons and from 6.8 to 7.1 in O. pedicornis at one side straw, and from 16.3 to 16.5 in O. cornifrons and from 13.3 to 13.5 in O. pedicornis at both sides straw. The sex ratio of Osmia spp. were from 1:1 to 1: 2.8 in O. cornifrons and from 1:2.8 to 1:5.5 in O. pedicornis. The sex ratio of O. cornifrons and O. pedicornis was different in 3 locations. The female and male cocoons of O. cornifrons were the long ellipticalshaped and grey-brown color. The width, length and weight of the female cocoon were 5.6± 0.6mm, 10.2±0.8mm and 89.5±20.0mg, respectively. The width, length and weight of the male cocoon were 5.0±0.4mm, 9.0±0.6mm and 62.1±11.3mg, respectively. The female and male cocoons of O. pedicornis were the long elliptical-shaped and polished dark-brown color. The female cocoon had the width of 6.5±0.6mm, length of 12.9±1.0mm and weight of 89.5± 20.0mg. In case of the male cocoon, the width, length and weight of were 5.0±0.4mm, 9.0± 0.6mm and 151.5±29.4mg, respectively. In both species of O. cornifrons and O. pedicornis, the cocoon size of the females was significantly larger than that of the male. Between those two species, the latter had a relatively bigger size than the former.