Preliminary Studies On Biological Characterstics And Males’Forming Mechanisms Of Phenacoccus Solenopsis Tinsley

In this paper, we examined the morphological characteristics, biological habits, effective accumulated temperatures and developmental threshold temperatures of Phenacoccus solenopsis Tinsley and Harmonia axyridis Pallas;studied on factors which effecting the male-female ratio of Phenacoccus solenopsis and differences between two reproduction modes; analyzed the feeding potential of Harmonia axyridis Pallas against Phenacoccus solenopsis Tinsley. The results are as followed:Under laboratory conditions, at18℃, Phenacoccus solenopsis Tinsley grows quite slowly with a33.3d’s generation development duration while it is reduced to10.4d at30℃condition and the developmental period of egg and larve are0.5±0.34d,4.3±0.51d,2.3±0.40d,3.3±0.50d, respectively. Preoviposition is7.9±0.09d. The lowest developmental threshold temperature appears at the first stage of larve (7.46℃) while the second instar larve needs the highest (14.74℃). The developmental threshold temperature and effective accumulated temperature of one generation is13.52℃,303.80day-degree in total.Amphogenic female adults’mean preoviposition and lifetime are8.9d and6.1d shorter than parthenogenetic adults’. Meanwhile, the amphogenic adults’mean egg laying amount is more than the parthenogenetic adults’. Amphogenic adults’filial generation also develops19.2%male adults which is significantly more than parthenogenetic adults’At90±3%RH condition, the mean ratio of male adult can reach50%in each group;the ratio of male adult(x) has significantly positive relationship with larve density(y), the liner equation is y=0.40x+20.037,r=0.790**. The light cycle of6L:18D condition develops25.6%fewer male adults than the light cycle of16L:8D, furthermore, the ratio of male adult(x) has significantly positive relationship with the light hours(y) as well,the liner equation is y=0.765x-2.095, r=0.853**.At30℃condition, Harmonia axyridis Pallas achieves the fastest development duration,24.4±0.68d. The Developmental threshold temperature of egg and larve are9.72℃,10.86℃,8.03℃,12.52℃,7.15℃,11.30℃, the effective accumulated temperature of egg and larve are41.02day-degree,47.64day-degree,34.51day-degree,28.17day-degree,92.55day-degree, 81.50day-degree, respectively. Harmonia axyridis Pallas’ mean daily consumption against Phenacoccus solenopsis Tinsley increases with Harmonia axyridis Pallas’instar; the ladybugs’ mean daily consumption against mealybugs are1.9,4.5,9.4,13.7,78.0, respectively.