The insect male accessory gland (MAG) is an internal reproductive organ responsible for the synthesis and secretion of seminal fluid components, which play a pivotal role in the male reproductive strategy. In many species of insects, the effective ejaculation of the MAG products is essential for male reproduction. For this purpose, the fruit fly Drosophila has evolved binucleation in the MAG cells, which causes high plasticity of the glandular epithelium, leading to an increase in the volume of seminal fluid that is ejaculated. However, such a binucleation strategy has only been sporadically observed in Dipteran insects, including fruit flies. Here, we report the discovery of binucleation in the MAG of the common bed bug, Cimex lectularius , which belongs to hemimetabolous Hemiptera phylogenetically distant from holometabolous Diptera. In Cimex , the cell morphology and timing of synchrony during binucleation are quite different from those of Drosophila . Additionally, in Drosophila , the position of the two nuclei in the adult stage changes as a result of the mating history or the nutrient conditions; however, it remains stable in Cimex . These differences suggest that binucleation in the Cimex MAG plays a unique role in the male reproductive system that is distinct from that of Drosophila .

Some diopsid flies have sexually dimorphic eye stalks that are assumed to require considerable nutrition for growth but are advantageous in competition and courtship. According to the handicap theory, the eye span in some dimorphic species serves as a reliable signal of individual quality to an opponent. However, it is not well understood how well eye span represents energy source storage. In this study, we focused on two species: Sphyracephala detrahens, which has weak dimorphism, and Cyrtodiopsis dalmanni, which has moderate dimorphism. We found that the eye stalks of the former species contained more fat bodies than those of the latter species. When the flies were starved, the fat body cells in the eye stalks underwent autophagy. A strong positive correlation was consistently found between eye span and starvation tolerance for S. detrahens, while a weak correlation was found for C. dalmanni. Furthermore, starvation decreased the contest winning rate between S. detrahens pairs with similar eye spans. These findings suggest that the presentation of resource holding potential may be larger than the actual storage ability and that the fidelity of nutritional storage signaling varies; the signal presented by S. detrahens is more reliable than that presented by C. dalmanni.