Observation of predation behavior and evaluation on predation capacity of Arma chinensis against Hyphantria cunea

  Objective  This paper aims to clarify the characteristics of predation behavior of Arma chinensis on Hyphantria cunea and evaluate the predation capacity of A. chinensis.

  Method  The predation behavior and predation capacity of adult and nymph of A. chinensis to the larvae of H. cunea were studied by means of indoor observation combined with the method of HollingⅡ disc equation fitting.

  Result  The process of predating could be divided into 4 kinds of behaviours: searching, piercing-sucking, waiting and feeding. The differences were extremely significant in searching time (P = 0.005) and piercing-sucking time (P = 0.002) among different groups. The searching time decreased with the increase of instar, and the feeding time increased with the increase of instar when the instar of A. chinensis was same. The ratio of A. chinensis piercing the stylet into the head of H. cunea larvae was significantly higher than thorax and abdomen (P = 0.001). We speculated that piercing into the head will be beneficial to controlling and killing larvae rapidly. The predatory functional response of 4th, 5th instar nymph and adult of A. chinensis to 3rd, 4th and 5th instar larvae of H. cunea was all agreed with the HollingⅡ disc equation (0.011 4−0.198 1 < χ²_0.05 = 9.49). The predation increased with the increase of prey density, and the searching effect decreased with the increase of prey density. The theoretical maximum daily predation of adult and 5th instar nymph of A. chinensis to 3rd instar larvae of H. cunea was all above 8 and the instantaneous attack rates of A. chinensis to 3rd instar larvae of H. cunea were all higher than 4th and 5th instar larvae. The predation of A. chinensis preying on 3rd larvae of H. cunea under bagging condition in forest after 7 days showed that: adult (6.60 ± 0.40) > 5th instar nymph (4.20 ± 0.58) > 4th instar nymph (2.40 ± 0.25).

  Conclusion  The adult and 5th instar nymph of A. chinensis have better predation capacity on the larvae of H. cunea, which could be used as a means of biocontrol against H. cunea.