The nesting behavior, reproduction, fruit set and shape of O. cornifrons varied significantly with the released sex ratio of O. cornifrons. A female : male sex ratio of 1 : 2 was resulted in a 3.4 to 6.7 fold higher than other sex ratio in a nesting behavior. A ratio of 1 : 2 resulted in a 1.2-fold nesting rate, which was slightly higher than other nesting rates. Releasing only males resulted in a 2.4-fold greater amount of fruit set in non-pollinated sites. A sex ratio of 1 : 2 gave a slightly higher shape index and a 1.2 to 1.6-fold lower asymmetric index than other sex ratios. There was no significant difference between female release numbers in fruit set, and 100 to 200 females gave a slightly higher shape index than 400 females. Thus, we determined that 200 females should be released per 2,000㎡ and that the sex ratio of females to males should be 1 : 2.

Osmia cornifrons is a cavity-nesting solitary species used as an apple pollinator in Korea. To elucidate the developmental characteristics of O. cornifrons, we investigated its development from the egg to adulthood, including a dormant prepupal phase and mating through indoor rearing (25 °C, 65% R.H.). The egg durations of the female and male bees were 3.6 ± 0.8 days and 3.1 ± 1.3 days, respectively. During larval development, the head widths of the 1st to 5th instars ranged from 0.7 ± 0.1 mm to 1.3 ± 0.1 mm. The peak of the growth in head width was the 2nd instar. The larval lengths ranged from 3.7 ± 0.6 mm to 13.6 ± 1.3 mm. The peak of growth was the 4th instar. The larval weights ranged from 4.5 ± 1.2 mg to 78.3 ± 16.1 mg. The peak of growth was the 3rd instars. The total larval durations of from the 1st to 5th instars for the females and males were 14.0 ± 6.0 days and 13.2 ± 5.8 days, respectively. The spinning durations of the females and males were 2.2 ± 0.7 days and 2.3 ± 0.8 days, the prepupation durations were 55.5 ± 5.9 days and 55.8 ± 2.9 days, and the pupation durations were 26.4 ± 2.1 days and 25.3 ± 2.3 days, respectively. The average longevity of the female adults and male adults was 21.8 ± 8.7 days and 24.4 ± 12.4 days, respectively. The total duration of from the egg to an adult bee of the O. cornifrons females and males was 123.5 days and 124.1 days, respectively. Mating consisted of the three following phases: the precopulatory (courtship and attempting copulation), copulation and postcopulatory phases. The mating times of the precopulatory, copulation and postcopulatory phases were 159.6 ± 288.9, 8.4 ± 7.1, 12.9 ± 4.5, and 198.8 ± 69.8 seconds.

Osmia cornifrons plays a major role in the pollination of orchards, but basic information on vitellogenin and the oocyte development is limited. To better understand vitellogenin in hymenopteran insects, we cloned a cDNA encoding vitellogenin from the hornfaced bee O. cornifrons. O. cornifrons vitellogenin cDNA contains 5477 bp with an open reading frame of 1,783 amino acid residues, and has a predicted molecular mass of approximately 200.21 kDa and a pI of 6.55. O. cornifrons vitellogenin possesses four consensus (RXXR/S) cleavage sites and has conserved DGXR and GL/ICG motifs in the C-terminus. The deduced amino acid sequence of the O. cornifrons vitellogenin cDNA showed a 66% identity with Megachile rotundata, 53% to Apis mellifera, 51% to Bombus ignitus, and 42%-30% with other hymenopteran insect vitellogenins. Phylogenetic analysis showed that O. cornifrons vitellogenin clustered with vitellogenins from Megachildae, Apidae, Vespidae, and Formicidae species but not with those from Pteromalidae, Aphelinidae or Ichneumonidae species.

The mason bee (Osmia cornifrons Radoszkowsky) is an excellent pollinator of apple. To understand geographic genetic variation of the species and relationships among populations sequenced a portion of mitochondrial COI gene, which corresponds to “DNA Barcode” region (658 bp) from 81 individuals collected over eight localities in Korea. The sequence data were used to investigate genetic diversity within populations and species, geographic variation within species, phylogeographic relationship among populations, and phylogenetic relationship among haplotypes. Summarized, overall moderate to low genetic diversity within populations and species was characteristic, concordant with the high potential to disperse of O. cornifrons in Korea. Although two populations were genetically subdivided from the remaining localities, no clear regional bias was observed. Overall, high rate of gene flow among localities and low FST was characteristic considering other relevant studies that investigated population genetic structure of other insects occurring in Korean peninsula.