Morphological study on the larvae of different instars of Bodilus gregarius (Coleoptera: Aphodiinae: Aphodiini)

The majority of species in the genus Bodilus (Aphodiinae, Aphodiini) are coprophagous, playing a crucial role in maintaining the cleanliness of the natural environment. However, compared with adults, research on the larvae of this group is significantly insufficient. In light of this, the present study focused on the larvae of Bodilus gregarius and used scanning electron microscopy (SEM) to provide the first detailed description of the ultrastructural features of larvae at different instars. It was found that the larvae of B. gregarius have three instars. After comparing the ultrastructures of the head, mouthparts, and anal sternite among larvae of different instars, it was revealed that the number of microsensilla at the tips of the antennae, the sensory spines attached to the anterior end of the hypopharynx, as well as setae on the frontal region of the head, labrum, and the raster of the anal sternite in the second- and third-instar larvae were much more numerous than those in the first-instar larvae. Meanwhile, the morphology of the stridulatory teeth differs among larvae of different instars, and only the third-instar larvae have an "X"-shaped depression on the surface of the labrum. The findings of this study not only provide effective data for the taxonomic research of larvae in the genus Bodilus but also offer fundamental data for revealing the evolution of morphological characteristics and ecological adaptability of small dung beetles.