Scathophaga stercoraria, commonly known as the yellow dung fly or the golden dung fly, is one of the most familiar and abundant flies in many parts of the Northern Hemisphere. As its common name suggests, it is often found on the feces of large mammals, such as horses, cattle, sheep, deer, and wild boar, where it goes to breed. The distribution of S. stercoraria is likely influenced by human agriculture, especially in northern Europe and North America. The Scathophaga are integral in the animal kingdom due to their role in the natural decomposition of dung in fields. They are also very important in the scientific world due to their short life cycles and susceptibility to experimental manipulations; thus, they have contributed significant knowledge about animal behavior.

Scathophaga stercoraria is sexually dimorphic, with an average lifespan of one to two months. The adult males are bright golden-yellow with orange-yellow fur on the front legs. Females are a little duller in color, with pronounced green-brown tinges, and no brightly colored fur on the front legs. The adults range from 5 to 11 mm in length, and the males are generally larger than the females. The physical features of separate S. stercoraria populations can vary greatly, due in part to the range of locations in which the species is found. Generally, they are located in cooler temperate regions, including North America, Asia, and Europe. They may also favor higher altitudes, such as the Pyrenees and Swiss Alps.

The adults mainly prey on smaller insects, mostly other Diptera. They can also consume nectar and dung as additional sources of energy. In a laboratory setting, adult S. stercoraria can live solely on Drosophila and water. Females spend most of their time foraging in vegetation and only visit dung pats to mate and oviposit on the dung surface. Both males and females are attracted to dung by scent, and approach dung pats against the wind. Males spend most of their time on the dung, waiting for females and feeding on other insects that visit the dung, such as blow flies. In the absence of other prey, the yellow dung fly may turn to cannibalism. The larvae are coprophagous, relying on dung for nutrition.

Scathophaga stercoraria breeds on the dung of many large mammals, but generally prefers fresh cattle dung. The operational sex ratio on these pats is very male-biased and competition is high. Females are small and have limited precopulatory choice. Copulation lasts 20–50 minutes, after which the male attempts to guard the female from other males. Both males and females often mate with multiple partners. Reproductive success depends on a variety of factors, including sperm competition, nutrition, and environmental temperature.

Females have paired accessory glands, which supply lubricants to the reproductive system and secrete protein-rich egg shells. Sperm is received in a large structure called the bursa copulatrix, and is stored in a structure called the spermatheca. Scathophaga species have three spermathecae, (one pair and one singlet), each with its own narrow duct that connects it to the bursa. Sperm can be stored in the spermathecae for days, weeks, or even years, and sperm from several males can be stored simultaneously. Males have two projections, the paralobes, which are used to hold onto a female during copulation. Between the paralobes is the intromittent organ, the aedeagus, which transfers sperm into the female's bursa copulatrix.

During copulation, sperm is not directly deposited into sperm-storing organs. Ejaculation occurs in the bursa copulatrix, and then females actively move sperm into the spermathecae using their muscular spermathecal invagination to pump sperm into transit. This gives females a level of control over which and how much sperm enters her system, an example of cryptic female choice. Although current results are inconclusive regarding whether or not females are cryptically selecting for a better phenotypic match, a female may benefit from having variable sperm fertilizing her offspring. Such adaptations are advantageous because females benefit from being able to control which sperm are successful in fertilizing eggs. The females may not be aware of which sperm are better suited for her offspring, but simply that being able to control the proportion of sperm from multiple mates can maximize the possibility of an optimal phenotypic match. It is to her advantage to have multiple males' sperm reach her eggs, rather than just one. After copulation, females prefer to lay their eggs on the small hills of the dung surface, avoiding depressions and pointed areas. This survival strategy aims to prevent desiccation and drowning so the eggs are placed where they have the greatest chance of surviving.

Many studies have studied the many manifestations of sexual conflict, including post-mating sexual selection, in the yellow dung fly. Sperm competition occurs when a female mates with multiple males. Each male's sperm is then in direct competition to fertilize the eggs. Sperm mix quickly once they reach the female's stores. The goal of males is to displace the sperm of other males as much as possible. Larger males tend to have longer copulation times and greater rates of sperm displacement. The fertilization success of males that were secondary mates increased as their body size relative to the first male increased.

Traits such as body size, testis size, and sperm length are variable, as well as heritable in S. stercoraria males. Larger sperm may be advantageous if they have greater propulsion along the female's spermathecal duct, resulting in higher fertilization success rates. When competition among males is high and females are mating with multiple males, those with the largest testes also have the most success in terms of proportion of sperm that fertilize a female's eggs. The resulting male offspring would then have a similar advantage.