| Latoia pastorlis (Butler) belongs to Lasiocampidae, Eucleidae. The larvae attaeked Sonneratia apetala Buch-Ham leaf, forming notch or holes, and eating up the whole leaves or the entire leaves on branches in outbreak, which seriously affected the growth of trees even led to the death of branchs. This paper systematieally studied on population structure characteristics, spatial distribution of larvae, morphological characteristics of each stage, life history and life habit of each stage of L. pastorlis (Butler) of pest on the S. apetala Buch-Ham. This paper also preliminary developed studied the prevention technology of this insect. The results were as follows:1. L. pastorlis (Butler) occurred for four generations each year in Qinzhou Kangxiling Mangrove Nature Reserve of Guangxi and had a phenomena of the generations overlap. It overwintered by pupa in cocoon and adult eclosion began in mid-April next year. By the end of April, the first generation of larvae appeared. There were four infestation periods of larvae occurred in a year. The fourth generation of larva produced cocoon and pupa and was in the overwintering status in the beginning of November.2. The newly hatched larvae of L. pastorlis (Butler) post hatch started moving and fed the residual eggshell, and fed the leaves of Sonneratia apetala Buch-Ham around eggshell. Over third instars larvae has a habit to feed the molting fresh skin. The larvae of L. pastorlis (Butler) fed on selectivity S. apetala Buch-Ham, Eucalyptus urophylla×E. grandis, and Kandelia candel, but didn t feed on Aegiceras corniculatum. This larvae liked the leaves of S. apetala Buch-Ham most. The feeding amount of the first instar larvae of L. pastorlis (Butler) was the least while the seventh instar larvae was the most which took64.27percent of the total, and the feeding amount of the fourth and the seventh instar larvae account for97.76 percent of the total. The average feeding area of all larval instars for host plant leaves of S. apetala Buch-Ham reached in269.1cm2per larva.The larvae of L. pastorlis (Butler) began to die in the forth day and that of most kept on surviving in eight days under the condition of no food. The survival rate of the larvae still reached97.78percent even it began to die after six hours with seawater immersion, however, it decreased to75.56percent after12hours.3. The spatial distribution of L. pastorlis (Butler) larvae was aggregation on four orientation of east, south, west and north of S. apetala Buch-Ham and implied individual group, and the distribution difference of all orientationwas not significant. Reasons for the aggregated distribution of L. pastorlis (Butler) larvae were environmental condition and aggregation nature of itself.4. The adults of L. pastorlis (Butler) activated during the night with phototaxis and were very quiet at day-time. The peak period of adult eclosion at night and the emergence number of night accounted for98.6percent of total, especially before midnight. Copulation occurred in the second day after eclosion and appeared between4:00-6:00in the morning and last about13-16hours. Oviposition occurred at night of the second day especially between22:00-02:00after the end of copulation. The fecundity form35to183eggs for female and its oviposition period was two to four days but normally was three days. The life length of adults is about six to eight days, and the average longevity of adults was about6.7days for male, and about8.1days for female.5. The adult, egg, larvae, and pupa or cocoon accounted for42.79%,47.6%,7.27%,2.34%;24.12%,32.77%,25.2%,17.91%;23.62%,34.68%,22.69%,21.05%;25.29%,32.44%,20.65%,19.58%, respectively of the age structure of L. pastorlis (Butler) in last April, form mid-June to early July, form mid-August to early September, and form mid-October to mid-November. The number were relative less for female compared with male in a year, and the female and male ratio was1:1.21.6. Four pesticides all had insecticidal effects on second or third instars larvae of L. pastorlis, of which30percent trichlorfon800,1000and1500times and25%benzoylphenal urea800times had the best control effect. Crystal trichlorfon with the concentrations of0.5,0.1,0.01mg/L and25%benzoylphenal urea8000,10000,15000times had little or no impact on shrimp, respectively.The innovative points of this article were that we systematieally studied on biological and ecological characteristics of L. pastorlis (Butler) of pest on the S. apetala Buch-Ham, as well as preliminary studied with the control techniques of this pest. |
PDF Full Text Request