Abstract: To study the developmental process of the reproductive system in the male adult of bumblebee Bombus patagiatus Nylander following emergence, semen volume, sperm count, gonad and spermatheca size of the reproductive system in virgin male adults at different day-old (1-15 day-old) were measured. The results showed that the volume of seminal fluid of drones at 1 day-old (5.95±0.39 μL) was maximal, while the sperm count of drones at 2 dayold reaches the peak under microscope. The number of motile sperms in the semen presented repeated wave trends. The motile sperm count (25.93±1.06) and the total number of sperm in the semen (160.67±17.11 ten thousand) reached the maximum at 9 day-old. The highest percentages of motile sperms were 86.38%±2.02% and 86.45%±2.50%, respectively, at 8 and 9 day-old. The length of gonad (1 522.01±37.93 μm) was minimum at 1 day-old. The middle width of spermatheca (86.38±2.96 μm) reached the maximum at 7 day-old, but had no significant difference with that at 9 day-old. The results indicate that the indexes of the reproductive system are relatively stable in drones at 8-9 day-old, and drones reach sexual maturity and could mate during this stage. The study provides a theoretical basis for artificial breeding of B. patagiatus.

Key words: Bombus patagiatus, male reproductive system, gonad, sperm, development