Antennal sensilla and compound eyes of fruit flies, Drosophila melanogaster (Meigen), Drosophila suzukii (Matsumura), Drosophila immigrans (Sturtevant), and Drosophila hydei (Sturtevant) (all Diptera: Drosophilidae), were observed with stereoscopic microscopy and scanning electron microscopy. The results showed that the antenna consists of 3 segments: a proximal scape, a pedicel, and a flagellum composed of a funiculus and a dendritic arista. Six morphologically distinct types of sensilla were observed on the antenna: chaetica, microtrichia, trichoid (Tr I, Tr II), basiconic, clavate, and coeloconic (Co I, Co II). Basiconic sensilla were significantly shorter than other sensilla in the funiculus of D. melanogaster. The number of clavate sensillae was less than other sensilla in the funiculus of D. melanogaster and D. immigrans, but was greater in D. suzukii and D. hydei. Moreover, coeloconic sensilla were absent in D. suzukii and D. hydei. The length and abundance of the chaetica sensilla on the compound eyes were different significantly among the 4 species. Drosophila hydei had chaotic sensilla with the greatest length and abundance; they were lowest for D. suzukii. Based on the previous literature, the possible functions of these sensilla are discussed. We inferred that fruit flies may regulate their behaviors according to the information detected by these sensilla.

Osmia excavata is an excellent pollinator in nature and plays a vital role in the conservation of agro-ecosystems and food security. Given the important role of the gut bacterial community in host health and regulation of host growth and development, using 16S rRNA gene sequencing data, the present study explored the composition of the gut bacterial community and its diversity at different life stages (eggs, young larvae, old larvae, young pupae, old pupae, and 1-day-old adults in cocoons) of the solitary bee Osmia excavata. The results showed that the core phyla in the gut of O. excavata at different life stages were Proteobacteria, Firmicutes, Bacteroidota, and Actinobacteriota, and the core genera were Sodalis, Tyzzerella, and Ralstonia. The highest intestinal bacterial diversity was found in the Egg period, and the lowest bacterial alpha diversity was found in the 1-day-old Adult period; the bacterial diversity of O. excavata showed a process of decreasing, as it was growing from the Egg period to the 1-day-old Adult period. Our study found that O. excavata undergoes a significant change in the structure of the gut flora when it grows from the young pupae to old pupae stage, a period of growth that coincides with the process of cocooning and isolation from the external environment after food depletion. This suggests that food and environmental factors are key contributors to the structure of the bacterial community in the gut of solitary bees.

The mason bee Osmia excavata Alfken (Hymenoptera: Megachilidae) is an essential pollinator for rosaceous fruit trees in northern China, but its populations are declining because of severe infestations by the mite Chaetodactylus hirashimai Kurosa (Acari: Sarcoptiformes). This mite feeds on pollen within mason bee nest tubes, thereby impairing larval development. However, the effects of different floral resources on the fitness of C. hirashimai remain unclear. Herein, we evaluated the development, survival, and reproduction of C. hirashimai reared on four diets (cherry pollen, cherry bee bread, apple pollen, or apple bee bread), by using an age-stage, two-sex life table. Chaetodactylus hirashimai successfully completed its life cycle on all diets. Cherry pollen supported shorter pre-adult development, longer adult longevity, and higher fecundity than apple pollen. Bee bread diets resulted in significantly lower pre-adult mortality (11.76–14.81%), and higher fecundity (270–278 eggs/female) and net reproductive rate (R₀ = 115–120 offspring/individual), than raw pollen (44.64–44.83% mortality; 117–179 eggs/female; R₀ = 40–50 offspring/individual). No significant differences in the intrinsic rate of increase (r) and finite rate of increase (λ) were observed among diets. Our findings demonstrated that cherry pollen is a highly favorable resource for C. hirashimai, and bee bread further enhances mite population growth. This study highlights the ecological conflict between cherry pollination and mite infestation, and these life-table results can provide preliminary laboratory support for subsequent research on integrated mite control in fruit orchards.