Obolodiplosis robiniae (Haldeman) is a specialist herbivore of Robinia pseudoacacia L., and its infestation is closely associated with tender leaf tissues. The ability of gravid females to recognize suitable host tissues is essential for successful oviposition and subsequent population development. Here, we assessed whether leaf age affects the host-selection behavior of O. robiniae and whether volatile organic compounds are associated with this process. Laboratory oviposition assays were used to compare egg deposition on tender leaves and mature leaves of R. pseudoacacia, and Y-tube olfactometer bioassays were performed to evaluate female responses to odors from the two leaf ages. Volatiles released from healthy tender leaves and mature leaves were collected using dynamic headspace sampling and characterized by thermal desorption–gas chromatography–mass spectrometry. Principal component analysis, orthogonal partial least squares discriminant analysis, and variable importance in projection scores were used to compare volatile profiles between leaf ages. Gravid females deposited significantly more eggs on tender leaves than on mature leaves in both choice and no-choice assays. Females also showed a significant olfactory preference for tender-leaf odors when directly offered a choice between volatiles from tender leaves and mature leaves, with 76.47% of responding individuals selecting tender-leaf odors and 23.53% selecting mature-leaf odors. Chemical profiling identified 28 volatile compounds across the two leaf ages, and their composition and relative abundance differed markedly. Among shared compounds, (Z)-3-hexen-1-ol and α-farnesene differed significantly between tender leaves and mature leaves. Multivariate analyses further identified several candidate compounds contributing to leaf age-related volatile differences. These results indicate that leaf age influences both oviposition behavior and odor-mediated host location in O. robiniae. Leaf age-dependent volatile blends may serve as important chemical cues associated with host selection by gravid females and provide a basis for future studies on volatile-mediated management strategies.

Despite the development of molecular techniques, morphological phylogeny still remains integral in underpinning the relationship between some clades of Calyptratae, especially the ones with fast radiation, such as those in Oestridae (Diptera: Brachycera), yet few synapomorphy has been proposed for adults in this family. Using scanning electron microscopy, we investigated the morphological structure and ultrastructure of the antennae and maxillary palps of adult Oestromyia leporina (Hypodermatinae, Oestridae). One type of trichoid sensillum (Tr), three types of basiconic sensilla (Ba I, Ba II, and Ba III), one type of coeloconic sensillum (Co I), and one type of clavate sensillum (Cl) were found on the antennal postpedicel. Surprisingly, this species has the most complex types of sensilla on the maxillary palps that have been reported in Calyptratae so far, with two types of coeloconic sensilla (Co II and Co III) and two types of mechanoreceptors. We then identified three common characteristics on the arista of Oestridae (Hypodermatinae, Oestrinae, Gasterophilinae and Cuterebrinae) that are potential synapomorphies. These characteristics indicate the value of the morphology of maxillary palps and aristae in taxonomy studies of Calyptratae.

The forest musk deer (Moschus berezovskii) is an endangered species endemic to China. Like many solitary and highly territorial herbivores, forest musk deer rely on chemical signals to convey complex information. However, the chemical composition and functional roles of these signals remain poorly understood. In this study, behavioral assays showed that forest musk deer (8 males and 26 females) exhibited stronger responses to urine than to feces. To characterize the chemical basis of this response, urine samples from five males and five females were analyzed using headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS), leading to the identification of 83 volatile compounds. Discriminant analyses revealed significant differences in urinary volatile profiles according to both sex and among individuals, with classification accuracies of 100% for sex and 96.7% for individual differentiation. Orthogonal partial least squares discriminant analysis (OPLS-DA) further identified 33 and 17 compounds that potentially convey sex-specific and individual-specific information, respectively, with only nine compounds implicated in both functions. These results suggest that forest musk deer employ a multi-layered coding system in chemical communication, in which distinct chemical compounds encode different types of biological information. Overall, this study provides a framework for understanding chemical signaling in captive forest musk deer and offers insights relevant to the conservation and sustainable management of musk deer populations.