Pogonus rodolphi Alluaud, a small semiaquatic carabid, lives in aggregation under rocks or in the wet soil along the margin of soda lakes in eastern Africa, including Kenya's Rift Valley region. The beetles migrate horizontally or vertically depending on the movement of the lake water, seeking an optimal temperature of 22–23°C and a soil humidity of 60–70%. They are mainly nocturnal and active throughout the year. Adults live for one year. Both sexes mate with several different individuals throughout life. The number of eggs per female is 20 at maximum, but because only one egg matures at a time and is deposited singly, the oviposition period lasts 5–6 mo. The main food is Spirulina platensis Nordst, a blue-green alga that thrives in soda lakes. There is one generation of this beetle a year. The spermatheca contains spermatozoa of 4–5 different males, which are discharged simultaneously into the vagina by capillary action of the seminal duct. Consequently, there is no sperm precedence in this species. However, the bursal system consisting of bursa copulatrix, bursal duct, and seminal duct is absent in newly emerged females. It appears suddenly when the first egg matures 2–3 wk after emergence and disappears after the second oviposition, 5–6 mo later. Eggs developed after this period are, therefore, unfertilized and are resorbed. Usually, there is only one bursa copulatrix per female, but sometimes there are 2, 3, or even 6. Also, the poor timing of the egg-sperm encounter often results in considerable sperm waste. From these facts, I hypothesize that the bursal system, which causes sperm nonprecedence, is a recent development and has evolved from a sperm-precedence system which still occurs in ≈6% of females.