Following to the former report (Harada et al., 1971), the survival and longevity of adult mosquitoes, Culex pipiens molestus and Aedes togoi, when fed on the flowers of 13 herbaceous and 5 woody plants were observed under laboratory conditions of room temperature during the period from April to September, 1971. Among the flowers of herbaceous plants tested, common vetch (Vicia sativa, Leguminosae) was most effective on the longevity of Culex, which had mean life-spans of 24 days in males and 28 days in females. The flowers of milk vetch (Astragalus sinicus, Leguminosae) which was tested with Aedes togoi was secondarily effective and the mean life-spans of them were 22 days in males and 17 days in females respectively. Rape (Brassica napus, Cruciferae), speedwell (Veronica persica, Scrophulariaceae) and sorrel vine (Cayratia japonica, Vitaceae) were all similarly effective on the survival and longevity of Culex or Aedes mosquitoes fed on these flowers and the maximum life-spans of them reached into a month or 40 days. The mosquitoes fed on the other flowers, such as dandelion (Taraxacum platycarpum, Compositae), cottonweed (Gnaphalium multiceps, Compositae) and fleabane (Erigeron philadelphicus, Compositae), reached into a month or more in their maximum life-spans but the greater parts of them died in about 10 days after the feedings. The survivorship curves of both male and female Aedes (and Culex) mosquitoes fed on the flowers of white clover (Trifolium repens, Leguminosae), stitchwort (Stellaria aquatica, Caryophyllaceae), houttuynia (H. cordata, Saururaceae), a kind of fleabane (Erigeron annuus, Compositae) and shepherd's purse (Capsella Bursa-pastoris, Cruciferae) were almost similar to that of the insects fed on plain water only and almost all died in 8-12 days after the feedings. Among the flowers of 5 woody plants, chestnut tree (Castanea crenata, Fagaceae) was most effective on the longevity of both male and female Aedes mosquitoes, about 80% individuals survived even after 25 days, and the next was Japanese privet (Ligustrum japonicum, Oleaceae), about 60% in males and 70% in females survived after 24 days respectively, and also the insects fed on the flowers of Japanese spindle tree (Euonymus japonica, Celastraceae) survived about 20% individuals after 30 days. In these cases, however, the maximum life-spans could not be seen owing to the shortage of the flowers which must be offered to the insects. Other woody plants, such as Japanese snowflower (Deutzia crenata, Saxifragaceae) and box tree (Buxus microphylla, Buxaceae) were fairly effective on the survival and longevity of Aedes mosquitoes. So it seems to be obvious that the flowers of woody plants including shrubs and arbors are more useful to maintain the insect life than that of the herbaceous plants in general. As a result of the surveys on the sexual differences of the longevities of both Culex and Aedes mosquitoes fed on 5 flowers it was found that male Aedes was longer than male Culex in the mean life-span as well as in the maximum lifespan. This suggests that the male Aedes mosquitoes suck nectar more actively than the male Culex. On the other hand, Aedes mosquitoes had 2 gonotrophic cycles even without any sugar solution but they could repeat 4 cycles under the feeding on 1% or 5% cane sugar solution. This finding suggests that, in natural conditions, adult mosquitoes must take nectar or some sugar containing fluids in order to repeat several gonotrophic cycles.
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