food intake. More specifically, optimal sperm production was measured at a 1:2 protein to carbohydrate ratio. Sperm fertility was best at a similar protein to carbohydrate ratio of 1:2. This close alignment largely factors in determining male fertility in Nauphoeta cinerea. Surprisingly, sperm viability was not affected by any change in diet or diet ratios. It's hypothesized that sperm viability is more affected by the genetic makeup, like in the "good sperm hypothesis". These ratios and results are not consistent with many other species and even conflict with some. It seems there can't be any conclusions on what type of diet is needed to positively influence sperm competition but rather understand that different diets do play a role in determining sperm competition in mate choice. Evolutionary consequences One evolutionary response to sperm competition is the variety in penis morphology of many species. For example, the shape of the human penis may have been selectively shaped by sperm competition. The human penis may have been selected to displace seminal fluids implanted in the female reproductive tract by a rival male. Specifically, the shape of the coronal ridge may promote displacement of seminal fluid from a previous mating via thrusting action during sexual intercourse. A 2003 study by Gordon G. Gallup and colleagues concluded that one evolutionary purpose of the thrusting motion characteristic of intense intercourse is for the penis to “upsuck” another man's semen before depositing its own. Evolution to increase ejaculate volume in the presence of sperm competition has a consequence on testis size. Large testes can produce more sperm required for larger ejaculates, and can be found across the animal kingdom when sperm competition occurs. Males with larger testes have been documented to achieve higher reproductive success rates than males with smaller testes in male yellow pine chipmunks. In chichlid fish, it has been found that increased sperm competition can lead to evolved larger sperm numbers, sperm cell sizes, and sperm swimming speeds. In some insects and spiders, for instance Nephila fenestrate, the male copulatory organ breaks off or tears off at the end of copulation and remains within the female to serve as a copulatory plug. This broken genitalia is believed to be an evolutionary response to sperm competition. This damage to the male genitalia means that these males can only mate once. Female choice for males with competitive sperm Female factors can influence the result of sperm