###### Abstract  
_Ecryptorhynchus scrobiculatus_ ([PERSON]) and _E. brandti_ ([PERSON]) are significant pests of tree of heaven, _Ailanthus altissima_, often leading to tree death. Monitoring systems that involve host-plant based attractants need to be developed for both insect pest species. Here, we compared the behavioral and electrophysiological responses of _E. scrobiculatus_ and _E. brandti_ to volatiles emitted by various parts of the host plant. Host plant-derived volatiles showed to play a greater role in the foraging behavior of _E. brandti_ than in _E. scrobiculatus_. Volatile components of phloem were found to be particularly attractive to _E. brandti_.  
B 2021 12 68 2021  
if two species differ slightly in their perception of host plants and ensuing foraging behavior, that may not be the case. Such subtle behavioral or sensory differences might facilitate subtle niche shifts and allow species with similar niches to coexist [4; 5].  
_Eucryptyrhynchus scrobiculatus_ ([PERSON]) and _E. brandti_ ([PERSON]) (Coleoptera: Curculionidae) are two closely related species of insect herbivores that feed on the tree of heaven, _Ailanthus altissima_ (Mill.) Swingle (Sapindales: Simaroubaceae). Both weevil species are host-specific and adults and larvae feed on different parts of _A. altissima_[6; 7; 8]. For instance, _E. scrobiculatus_ adults feed on annual branches, perennial branches, and petioles, whereas the larvae feed on the root system. In contrast, _E. brandti_ adults feed on the trunk, and larvae develop under the bark, destroying the phloem and xylem as they feed [9; 10; 11; 12]. The simultaneous occurrence of the two weevils causes extensive damage to _A. altissima_, commonly leading to tree death [10; 13; 14].  
Developing effective pest management methods for _E. scrobiculatus_ and _E. brandti_ involving the application of insecticides [15; 16] and novel trapping systems [17; 18] has been the focus of recent research. In terms of trapping, previously, [PERSON] et al. [17] found that a mixture composed of vinegar, ethanol, and apple juice was attractive to _E. scrobiculatus_. However, this attractant was not deemed feasible for mass production because it was made of fresh materials, resulting in a short span of attractiveness. Recently, trunk trap nets for _E. scrobiculatus_ and adhesive trunk trap nets for _E. brandti_ were developed [14; 17; 18; 19]. Trunk trap nets would be more effective if attractants were made available. In order to develop effective attractants for both _E. scrobiculatus_ and _E. brandti_, it is important to understand the role that volatiles of _A. altissima_ play on the olfactory response of both weevil species. Previous observations (Wen, unpub. data) indicated that _E. scrobiculatus_ and _E. brandti_ congregate on the bare phloem of tree of heaven in the field, regardless of whether the trees are healthy or injured. Based on these observations, we inferred that volatiles from bare phloem may be attractive to the weevils.  
The main goal of this study was to explore the role of host volatiles in the foraging behavior of _E. scrobiculatus_ and _E. brandti_. In particular, we compared the effects of bare phloem from healthy and injured trees and volatiles emitted by different parts of host plant on the behavioral response of the weevils. In addition, volatile compounds emitted by different parts of _A. altissima_ were collected by two methods (headspace solid phase microextraction (HS-SPME) and dynamic headspace method) and analyzed by gas chromatography-mass spectrometry (GC-MS). Finally, the antennal responses of _E. scrobiculatus_ and _E. brandti_ to selected chemical compounds were examined by electroantennography (EAG) and behaviorally using Y-tube olfactometer. These results may provide a reference for the development of attractants that are based on host-plant-derived volatiles.