The Flesh Fly: Sarcophaga crassipalpis

Form and Function

            Sarcophaga crassipalpis, as a member of the Sarcophagidae family, is gray in color with three black stripes on the body and a red tip on the posterior end. Adults are marked by a black strip framed by vertical yellow bands between the eyes (Diaz & Kaufman 2011). For more information on how S. crassipalpis is distinguished from other species, see Classification.

            S. crassipalpis shows a degree of sexual dimorphism. Males are hairier than females. They also have stronger, more powerful legs, which allow them to dominate their mate during copulation (Diaz & Kaufman 2011). This is extremely important in S. crassipalpis Reproduction. For more information on the general anatomy of the flesh fly - as well as some incredible pictures - visit the UF IFAS Featured Creatures page.

            Members of S. crassipalpis are extremely well-adapted to their environment. As a constituent of the Insecta class, they have a lightweight chitinous exoskeleton called a cuticle during their larval stage (Vincent & Wegst 2004). Although not unique to the species in question, the cuticle is integral to the success of all flies and even insects in general. (Examples include the flower fly and the mayfly.) The cuticle is secreted by a layer of epidermal cells that covers the entire external surface of the insect. It performs roles not limited to protection: it also provides support and shape, allows for movement, performs water-proofing and diffusion control, and serves as a barrier against potentially harmful organisms - parasites, vectors, and disease-causing microorganisms (Vincent & Wegst 2004). It does all of this despite a number of obstacles. First, the cuticle must resist wear even through near-constant strain, especially around the mouth. Second, it must be firm enough to provide adequate protection to the fly’s delicate innards while still maintaining the elasticity required for locomotion. And third, it must adapt so as not to obstruct the senses of the insect from the external world (Vincent & Wegst 2004). Thus the cuticle is one of the most significant adaptations ofS. crassipalpis and of all insects.

            Some S. crassipalpis pupae exhibit another incredible adaptation: they undergo the process of diapause, a period during which their development into adulthood is suspended during unfavorable environmental conditions. This is also sometimes referred to as overwintering. Larvae prepare to diapause by burrowing into the ground before entering the stage. The pupae can remain underground for up to six months, in the meantime facing subzero temperatures, irregular soil moisture, and the presence of ice (Kelty & Lee 2000). Not all members of S. crassipalpis diapause, as those that develop during the warmer seasons have no need, but studies show that those that do exhibit more resistance to freezing overall. While the pupal cuticle offers little to no freezing resistance, the puparium – basically a secondary cuticle – contains lipids on its inner surface that prevent water loss and help to inhibit freezing. Furthermore, the inside of puparia of diapausing pupae is line with three times as many lipids as that of non-diapausing pupae. However, the likelihood of a pupae experiencing death by frigid temperatures increased with exposure time, whether diapausing or not (Kelty & Lee 2000).

            Nevertheless, non-diapausing pupae are not entirely helpless during the cold season. Continuous freezing temperatures tend to kill flies within twenty-five days, but even a brief exposure to warm temperature during that time increases the survival of S. crassipalpis. Such warmth stimulates heightened levels of ATP, which increases the flies’ ability to perform metabolic processes such as volume regulation and nutrient uptake. This ability to avoid freezing even in non-diapausing pupae probably evolved because of the flies’ regular exposure to alternating low and high temperatures (Dollo et al. 2010)

            Read on to learn more about the Life History and Reproduction, including a more in-depth look at the developmental stages of S. crassipalpis. Or click here to return to the home page.