Blowflies, also known as blow flies, are a type of fly belonging to the family Calliphoridae. The name “blowfly” comes from the old English term “blawan,” which means “to blow or to swell.” The name is thought to be derived from the bloated appearance of carcasses that blowflies often feed on and lay their eggs in.
Blowflies are attracted to decaying organic matter, including animal carcasses, feces, and rotting food. The term “blow” in “blowfly” also refers to the buzzing sound that these flies produce when they fly.
- Color: Adult blow flies are often metallic, while larvae are pale in color.
- Characteristics: Adults have sponge-like mouth parts, with feathery hairs on the terminal antennal segments of the males. Larvae have hook-like mouth parts.
- Larvae: Blow fly larvae are also known as maggots. Measuring 9 to 22 mm in length, maggots are equipped with hook-like mouthparts and spiracles for breathing. They are soft and appear similar to worms or grains of rice. Each body segment of the blow fly maggot has a median row of fleshy tubercles that resemble hair.
The sound is created by the rapid beating of their wings, which can be quite noisy. This buzzing noise is distinctive and can help identify blowflies. Blowflies play an important role in the ecosystem as decomposers. They are among the first insects to arrive at a dead animal carcass, and they help break down the decaying matter by consuming it and laying their eggs.
The larvae, known as maggots, feed on the decaying material, accelerating its decomposition. The name “blowfly” is widely used in English-speaking countries, but it’s worth noting that different species of blowflies may have different common names in various regions.
Blow flies are found worldwide, occurring in almost every place occupied by people. In North America, the most common blowfly species is the green bottle fly (Lucilia sericata), while in Europe, the blue bottle fly (Calliphora vomitoria) is often referred to as a blowfly.
Adult blowflies are occasional pollinators, being attracted to flowers with strong odors resembling rotting meat, such as the American pawpaw[1] or dead horse arum[2]. Little doubt remains that these flies use nectar as a source of carbohydrates to fuel flight, but just how and when this happens is unknown.
Predators of blow flies include a variety of insect and bird species that feed on them or their larvae. Insects such as parasitic wasps (e.g., Pteromalidae and Tachinidae)[3] are known to parasitize blowfly larvae, laying their eggs on or inside them, which eventually leads to the death of the larvae. Some beetles, ants, and spiders also prey on blowfly eggs and larvae.
Additionally, certain bird species, including chickens, particularly those with insectivorous diets, may consume adult blowflies as part of their foraging behavior. For example, swallows (Hirundinidae), flycatchers (Muscicapidae), and certain species of birds in the Corvidae family[4] have been observed feeding on blowflies. These predators help regulate blowfly populations and contribute to the overall balance of the ecosystem.
Blow flies do not bite humans, though they are significant carriers of bacteria and germs. These flies can be dangerous to animals, however, if they are able to fester in and lay eggs in a wound or sore an animal may be carrying. The feeding larvae exacerbate existing wounds, and can end up making the animal very sick, and may even cause the animal to die if left untreated. Female Blow flies may also lay eggs in an animal’s eyes, ears, or nose.
Compound eyes are the types of eyes that most arthropods have. These eyes consist of thousands of photoreceptors that help the vision of insects and crustaceans. Almost all species of insects like flies and bees have these compound eyes. A compound eye forms a three-dimensional image which is a combination of thousands of images received by thousands of photoreceptors present in a single compound eye.
Blowflies have a significant connection to the field of forensic science, specifically in the area of forensic entomology[5]. Forensic entomology is the study of insects and other arthropods in relation to legal investigations. Blowflies are often the first insects to colonize a decomposing body, attracted by the strong odor of decaying flesh. By studying the life cycle of blowflies and the stage of development of their larvae (maggots) found on a corpse, forensic entomologists can estimate the time since death, known as the postmortem interval (PMI).
They can also gather information about the circumstances surrounding the death, such as whether the body has been moved or if there is evidence of trauma. Forensic entomology involving blowflies has been utilized in criminal investigations, mass disaster scenarios, and cases involving suspicious deaths.
The knowledge of blowfly biology, behavior, and development patterns helps forensic investigators obtain valuable insights into the timeline and circumstances of a death, particularly when traditional methods may not be sufficient.
Footnotes
- The American pawpaw (Asimina triloba) is a small deciduous tree native to the eastern and central United States. It belongs to the Annonaceae family, which also includes tropical fruit trees like cherimoya and soursop. The American pawpaw tree typically reaches a height of 10 to 40 feet (3 to 12 meters) and produces large, oblong-shaped leaves. It bears fruit known as pawpaws, which are the largest edible fruits native to North America. Pawpaw fruits are greenish-yellow when ripe and have a custard-like texture with a tropical flavor reminiscent of banana, mango, and melon. The fruits are highly valued for their unique taste and are used in various culinary applications, such as desserts, smoothies, and ice creams. The American pawpaw tree thrives in moist, fertile soils and is an important component of certain ecosystems, providing food and habitat for wildlife. It is also gaining popularity as a cultivated fruit tree in backyard gardens and orchards. [Back]
- The dead horse arum (Helicodiceros muscivorus), also known as the dead horse lily or corpse flower, is a unique and intriguing plant species. Native to the Mediterranean region, this perennial herb belongs to the Araceae family. The dead horse arum gets its peculiar name from its strong and foul odor, which resembles the scent of rotting flesh. The plant produces a large, maroon-colored inflorescence that can reach up to 1 meter (3 feet) in height. The flowers have a distinctive shape and pattern, with a long central spadix covered in tiny flowers and a surrounding spathe that gives it the appearance of a horse’s head. The odor serves as an attraction mechanism to lure in carrion flies, which are the primary pollinators of the plant. The dead horse arum’s fascinating characteristics make it a subject of curiosity and interest among botanists, horticulturists, and plant enthusiasts. [Back]
- Parasitic wasps, such as those belonging to the families Pteromalidae and Tachinidae, are a diverse group of insects known for their parasitic lifestyles. These wasps have evolved to parasitize a wide range of host organisms, including other insects. The Pteromalidae family comprises small to medium-sized wasps that typically parasitize the larvae or pupae of other insects, such as beetles, flies, and moths. They lay their eggs on or near the host, and the wasp larvae feed on the developing host, ultimately leading to its death. Tachinidae, on the other hand, is a large family of flies that are considered parasitoid wasps. They lay their eggs on or inside the bodies of various host insects, including caterpillars, beetles, and true bugs. The Tachinidae larvae then consume the host from within, eventually killing it. Parasitic wasps, including those from the families Pteromalidae and Tachinidae, play a crucial role in biological control, as they help regulate populations of pest insects in natural ecosystems and agricultural settings. [Back]
- Birds in the Corvidae family, commonly referred to as corvids, are a diverse group of intelligent and adaptable birds known for their distinctive characteristics. Corvids include well-known species such as crows, ravens, magpies, and jays. They are typically medium to large-sized birds with stout bodies, strong beaks, and often glossy black plumage. Corvids are highly intelligent and exhibit complex social behaviors, problem-solving abilities, and tool use. They are omnivorous, feeding on a wide range of food sources, including fruits, seeds, insects, small vertebrates, and carrion. Corvids are known for their vocalizations, displaying a wide range of calls, songs, and mimicry abilities. They are found in diverse habitats worldwide, from forests to urban areas, and their adaptability has contributed to their successful colonization of various environments. Corvids play important ecological roles, including seed dispersal, insect control, and scavenging, and they have cultural significance in many societies throughout history. [Back]
- Forensic entomology is a branch of forensic science that utilizes the study of insects and other arthropods to aid in legal investigations. It involves the application of entomological knowledge and techniques to determine the time of death (postmortem interval), identify the location of death, and gather other relevant information in criminal cases or suspicious deaths. Forensic entomologists analyze the presence, life cycle stage, and behavior of insects found on or near a body, as well as the environmental conditions surrounding the scene. By examining factors such as insect succession, insect biology, and the effects of decomposition on arthropod colonization patterns, forensic entomologists can provide valuable evidence and insights to assist law enforcement agencies and the justice system. [Back]
Further Reading
Sources
- “The use of insects in forensic investigations: An overview on the scope of forensic entomology” (July-December 2011) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3296382/
- Byrd, J. H., & Castner, J. L. (2010). Forensic entomology: the utility of arthropods in legal investigations (2nd ed.). CRC Press.
- Wall, R. (2001). The Biology of Blood-Sucking in Insects (2nd ed.). Cambridge University Press.
- Greenberg, B. (1991). Flies as forensic indicators. Journal of Medical Entomology, 28(5), 565-577.
- National Park Service. (n.d.). Asimina triloba (Linnaeus) Dunal – pawpaw. Retrieved from https://www.nps.gov/plants/pubs/chesapeake/plant/254.htm
- The Pawpaw Foundation. (n.d.). About pawpaws. Retrieved from https://www.pawpaw.kysu.edu/pawpaw/about.htm
- Royal Horticultural Society. (n.d.). Helicodiceros muscivorus. Retrieved from https://www.rhs.org.uk/Plants/3708/Helicodiceros-muscivorus/Details
- Kite, G. C., Hetterscheid, W. L. A., & Lewis, C. E. (2019). Helicodiceros muscivorus. In The Genus Arum (pp. 61-65). Royal Botanic Gardens, Kew.
- The Botanical Society of America. (n.d.). Helicodiceros muscivorus. Retrieved from https://botany.org/PlantChecklist/EuroHerb.php?ID=4434&name=Helicodiceros%20muscivorus
- O’Hara, J. E. (2002). Tachinidae Resources. Retrieved from https://www.nadsdiptera.org/Tach/home/Tachhome.htm
- Boarman, W. I., & Heinrich, B. (1999). Common Raven (Corvus corax). In The Birds of North America (P. G. Rodewald, Ed.). Cornell Lab of Ornithology. Retrieved from https://birdsna.org/Species-Account/bna/species/comrav/introduction
