## 1 Introduction  
An agroecosystem includes the food web and infochemical web, in which pests and predators utilize chemical information to search for food resources [1]. Host plants play a bridging role among the plant-prey-natural enemy tritrophic system. Plants provide habitat, food and refuge for pests and their natural enemies, and they also transfer basic communication information between the pests and natural enemies [2]. Plants are frequently attacked by all kinds of herbivores, including chewing-feeding and sap-feeding pests, and the pests not only result in physical wounds but also trigger underlying plant defense responses. Injured plants can release volatiles, known as herbivore-induced plant volatiles (HIPVs), to attract predators and parasitoids [3]. The primary functions and mechanisms of HIPVs in tritrophic interactions have been reviewed in detail [4].  
Abundant evidence has proved that HIPVs play an important role in parasitoids locating hosts, and increasing amounts of data have also confirmed that HIPVs can attract predators.  
Aphid-induced plant volatiles were found to attract the ladybeetles _Harmonia axyridis_ ([PERSON]) (Coleoptera: Coccinellidae), _Coccinella septempunctata_ ([PERSON]) (Coleoptera: Coccinellidae) and _Propylaea japonica_ ([PERSON]) (Coleoptera: Coccinellidae) [5; 6; 7]; the emission of volatiles by citrus trees to repel _P. japonica_ when infested simultaneously by _Diaphorina citri_ Kuwayama (Hemiptera: Psyllidae) and Citrus Huanglongbing [8] was also detected. However, little is known about how whitelfly-infested plants affect the performance of predatory ladybeetles [9].  
The cotton whitefly _Bennisia tabaci_ (Gennadius) Middle East-Asia Minor 1 (MEAM1, commonly known as B biotype) (Hemiptera: Aleyrodidae) is a major pest of many agronomic and horticultural crops, infesting more than 600 host plant species and causing great economic losses to agricultural production [10]. _Bennisia tabaci_ has a high resistance to most pesticides, which causes concerns regarding the excessive use of insecticides. Therefore, biological control has been considered as a safe and sustainable way to alleviate the damage of _B. tabaci_. The biological control agents of _B. tabaci_ include parasitoids, predatory ladybeetles, pathogenic microorganisms and so on [11; 12; 13]. The ladybeetle _Serangium japonicum_ Chapin (Coleoptera: Coccinellidae) is a strong predator of whiteflies, and the adults have a lengthy longevity and high fecundity [12; 14; 15]; thus, the ladybeetle has drawn much attention regarding the control of _B. tabaci_[12; 16; 17; 18].  
Plants grow in complex multi-species communities, so natural enemies are always confronted with a mixture of plant odors. We hypothesized that different host plant species of _B. tabaci_ might affect the orientational choice of _S. japonicum_ as the ladybeetle locates its prey by using volatiles from their prey or prey-infested host plants, which may affect the biological control efficiency of _S. japonicum_ against _B. tabaci_. Therefore, we studied (1) the preferences of _B. tabaci_ and its natural enemy _S. japonicum_ adults for different plants in greenhouse cage experiments, (2) the responses of _B. tabaci_ and _S. japonicum_ adults toward different host plants in a wind tunnel, (3) the performance of _S. japonicum_ in a Y-tube olfactometer and (4) the volatiles collected from plants. The present work provides valuable information for the maximization of the biological control efficiency when utilizing _S. japonicum_ to control _B. tabaci_ in different plant species. In view of the current results, we also propose a new strategy--i.e., an eggplant + _B. tabaci + _S. japonicum_ system--to control _B. tabaci_ damage in the integrated management of whitefly.