田间蜘蛛集团对飞虱的每日捕食量与室内、盆栽水稻的捕食作用比较

Comparison of Daily Predation of Rice Planthoppers by Spiders with Their Predatory Effect in Laboratory and Caged-rice

采用控制论中的脉冲采样法结合杀死飞虱计数法研究了田间蜘蛛对飞虱的每日捕食量估计并与室内、盆栽罩笼水稻功能反应的捕食作用进行了比较。结果表明田间蜘蛛平均每头每日对飞虱的捕食量为 0 .669头 ,这一捕食量比室内和盆栽水稻的捕食量要小得多 ;田间捕食百分率与飞虱密度呈二次抛物线关系 ,即飞虱低密度和高密度捕食百分率均低于中等密度 ,在每穴 1 0头飞虱左右 ,捕食量和捕食百分率最高。在有一定存量蜘蛛时 ,捕食量与微蛛、狼蛛数量呈显著的二元线性回归关系 ,但偏相关系数为负。由此表明随蜘蛛密度的增加捕食量反而下降 。

Spiders are important predators to planthoppers in paddy field. There are many reports on predation function of the predator. But it is still difficult to estimate number of insects predated by natural spider population group owing to their generalist, interference of inter\| and intra\|species, and error of planthopper numbering. However, relative accurate estimation of the insects predated has practical and important meanings for forecasting planthopper occurrence, making control decision, and augmenting natural control of natural enemies. The daily predation number of field spider group to planthoppers was studied by pulse sampling (succession of predators and insect pests is considered as a cybernetics system, sampling data at any time as a representative of characteristic of the system). Planthoppers were killed by 50% dichlorvos (diluting 800 times using water) at 20 min before numbering to ensure accurate of planthopper observation. Sixty hills were randomly sampled and the numbers of planthoppers and predators and other preys were recorded. Predatory effect in functional response of spider in laboratory and on caged rice in pot were compared with that of field population predation in this paper. The number of planthoppers preyed was calculated by the following equation:\$\$ Y t=(N t+H t+M t)-(N t+1 +P t+E t+D t)\$\$Where Y t is predation number of spider group; N t and N t+1 are planthopper number at time t and t +Δ t (Δ t =one day), respectively; H t, M t, E t, P t and D t are numbers of hatched nymphs, immigrated and emigrated adults, parasitized nymphs and adults, and natural death during t to t +Δ t , respectively. Some of the above parameters were determined by supplementary tests. H t was obtained by pulling twenty hills of rice at the same time of sampling, transplanting in pots, and recording number of nymphs hatched till next day. P t was determined by catching 100 nymphs from paddy field, raising in laboratory during t to t +Δ t , observing number parasitized ( P n) (P t=P n /100×100). M t and E t were by following methods, if fifth instar nymphs are not recorded at time t , the adults at t +Δ t (next day) are considered as immigrants ( M t =number of adults at t +Δ t ); The determination of emigrants are different from that of immigrants. Ten frames made of four bamboo poles, tying plastic film (50cm×50cm) to the top, were randomly caged above rice plant canopy. The adults adhered to the plastic film, spreading petrolatum toward plant canopy, were thought to be emigrants. Sixty hills were sampled every day and numbers of planthoppers, spiders and other species were recorded. Comparison of predation number of field spiders to planthoppers was made with that of functional response in laboratory and on caged rice in pot. \; The result showed that predation number was not positive correlation with planthopper and spider densities in table 1. The number was maximum at middle planthopper density (about 10 hill -1 ). Data analysis from pulse sampling indicated relationship between predation percentages ( Y ) and planthopper density per hill ( x ) was fitted by a parabola, the equation was as followisY=0.27241+0.002996x-0.000136x 2±0.139445From that equation, it was confirmed that the predation percentage at low and high density of planthopper was lower than that at the middle (about 10 planthoppers per hill). The relationship of Y with two dominant taxa (Micryphantidae and Lycosidae) was constructed as following binary linear regression equation:Y = 0.62064 - 0.0667 (±0.012187)x 1 - 0.19116 (±0.0288521)x 2 ±0.08519Where x 1 is Micryphantidae, x 2 is Lycosidae. Their regression coefficients were negatives, indicating that predation number decreased with increase of the spider density. It had been confirmed by multi\|predator coexistence system and field cage experiments.\; Daily average consumptive planthopper per spider in pa