| At present, the mainly studying of foraging behavioural ecology is about ladybird and lacewing, and less about aphidophagous hoverfly. The predaceous syrphid fly, Episyrphus balteatus De Geer is one of the significant predators for the control of aphides. In this paper, predation, starvation endurance ability, foraging behavior of E. balteatus and the effect of different aphides on its growth and development, have been studied. The main results are as follows:1. The functional response of the first, second and third instar larvae of E. balteatus preying on Macrosiphum avenae (F.) show the Rolling II type with better fitting. The daily maximum number of M. avenae preyed theoretically by the first, second and third instar larva of E. balteatus are 5.13,26.00 and 119.26 aphids respectively.2. There are mutual interference among the third instar larvae of Episyrphus balteatus De Geer , and the searching efficiency decreases and the intensity of scrambling competition increases with increase of its density. The best searching densities of the first, second and third instar larva of E. balteatus are 6.73,10.09 and 44.03 aphids respectively.3. The predation ratio of E. balteatus is the lowest at 14 癈 and the predation ratio at 18 C, 22 C, 26 C and 30 C are not different. Space heterogeneity has the great effects on predation of E. balteatus. The more wheat leaves the larvae encounter, which means more interference is met during predation, the lower the predation efficiency is observed.4. In the situation of lack of prey, the average survival time of E. balteatus larvae, whose growth stages are 0 h, 24 h, 48 h and 72 h, are 1.53 d, 2.48 d, 3.06 d and 3.75 d respectively. The higher starvation endurance ability is beneficial to the increase of survival opportunities, the increase of opportunities encountering prey as well as the control of aphid.5. The E. balteatus larvae fed by Brevicoryne brassicae (Linnaeus) can not complete their individual development. The larvae fed by Macrosiphum avenae (F.), Rhopalosiphumpadi (L.), Myzus persicae (Sulzer) and Aphis citricola have not some difference on the larva weight, the pupa weight, growth and development.6. The most frequent sequence of the foraging behavior of E. balteatus is: searching ?capture ?consumption - cleansing - break - searching.7. The searching behavior of the third instar larva of E. balteatus has been studied. The results show that the total rectilinear distance between stops in 0-15, 15-30, 30-45, 45-60 and 60-75 seconds before feeding is significantly longer than that after feeding respectively. The searching speed in 0-15,15-30, 30-45,45-60 and 60-75 seconds before feeding is 1-4 times quicker than that after feeding, which varies very little before feeding, but the longer the time is after feeding, the quicker the searching speed is. The total rectilinear distance from food to stops is significantly longer and the searching area covered by the larvae is 3-12 times larger before feeding than after feeding. It is believed that the search behavior of the third instar larva of E. balteatus De Geer is extensive search before feeding, and is area-concentrated search after feeding.8. Contacting with aphid, eating an aphid and contacting with agar block with aphid body fluid on it can arouse searching behavior of E. balteatus De Geer larva from extensive search to area-concentrated search , and contacting with agar block can not. The GUT has been measured after each of the following 4 feeding stimuli was provided: a) eating a large aphid; b) eating a small aphid; c) at first, eating a small aphid, continuously a large aphid; d) at first, eating a large aphid, continuously eating a small aphid. The deference between the GUT after 4 feeding stimuli are not significant. It is believed that the GUT is not determined by the time, the amount or the size of the prey consumed.9. The foraging behavior of E. balteatus De Geer larvae changes gradually at different aphid densities. When the aphid density changed from low to high, the... |
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