Cochliomyia macellaria

Distinguished from the closely related primary screwworm Cochliomyia hominivorax by three key features: (1) pale setae on fronto-orbital plate versus black hairs in C. hominivorax; (2) central black thoracic stripe extends well in front of the mesonotal suture versus only slightly in front in C. hominivorax; (3) larvae lack pigmented tracheal trunks and possess V-shaped spines on the anal protuberance versus pigmented tracheal trunks in C. hominivorax. C. macellaria larvae also lack an oral sclerite present in C. hominivorax.

Associated with carrion and decomposing organic matter in terrestrial environments. In the Pantanal region of Brazil, most abundant in open pasture areas with sparse trees (35.57% of captures) compared to forested savanna (8.07%), likely due to better bait odor dispersion in open areas. Predominantly rural in distribution (97.96% of captures in one study) versus urban (1.37%) and forested (0.69%) areas. Found in slaughterhouses, outdoor markets in tropics, and areas with garbage accumulation.

Americas from southern Canada through the United States, American tropics, and southern South America to Patagonia, excluding Chile and Argentina. Most common in southeastern United States (Florida, Louisiana, Georgia). Present in Caribbean Islands, Central America, and northern South America. Also recorded from Galápagos Islands and West Indies. GBIF records confirm presence across Brazil in multiple states including Amazonas, Pará, São Paulo, and Rio Grande do Sul.

Year-round activity in tropical and subtropical regions. In Southern Pantanal, Brazil, exhibits bimodal population peaks: May–July (late autumn/early winter) and October–December (spring). Population increases during periods of extended rainfall. In southeastern United States, adults attracted to dead tissue within minutes of death in some regions, with 24-hour delay in other regions.

Larvae feed exclusively on necrotic (dead) tissue and decaying flesh of animal carcasses. Adult males feed on vegetation and nectar from flowers. Adult females feed on tissue fluids from live wounds and necrotic tissue, requiring protein for egg development.

• cattle - livestock host for myiasislarvae infest wounds and necrotic tissue; causes secondary cutaneous myiasis
• humans - accidental hostcan cause myiasis in wounds

Complete metamorphosis with four stages. Eggs: laid in groups of 40–250 on carrion or wounds; approximately 1 mm, white to pearl white; hatch in 4–24 hours depending on temperature and moisture. Larvae: three instars over 4–7 days; feed on necrotic tissue; third instar reaches 17 mm; fall from food source to pupate in soil. Pupae: formed in top layer of soil, leaves, or garbage; outer skin hardens and turns brown; duration 7 days to 2 months depending on temperature. Adults: emerge after 1–2 days maturation; sexually mature within 4 days; lifespan 2–6 weeks; females may lay 1000+ eggs in lifetime.

Females release pheromones that stimulate male copulatory attempts on contact. Males mate rapidly and remain near females during mating period, staying within a couple meters. Females travel long distances to find mates and oviposition sites. Females commonly oviposit in aggregations with other females, leading to thousands of eggs on single carcasses. No parental care provided by either sex; females strategically oviposit in dead tissue to ensure larval nutrition. Exhibits oviposition preference for aged carcasses over fresh carrion, with higher oviposition after 8-hour exposure time. No preference shown between previously colonized or uncolonized carcasses.

Specialist carrion decomposer facilitating nutrient recycling and removal of carcasses and organic wastes. Serves as prey for other organisms including competing calliphorid larvae (Chrysomya albiceps larvae have been observed attacking C. macellaria larvae). Acts as vector for eggs of Dermatobia hominis (human bot fly), contributing to economic losses in livestock. Important indicator species in forensic entomology for estimating postmortem intervals and determining time of colonization.

Forensic importance: most common blow fly on carrion in southern United States; used for postmortem interval estimation in criminal investigations. Medical-veterinary importance: causes secondary myiasis in livestock and humans; poses economic risks to cattle industry through wound infestation and disease transmission (carries Salmonella and swine influenza virus). Maggot therapy potential: larvae consume necrotic tissue and secrete antibacterial compounds, though less commonly used than Lucilia sericata. Management requires proper carcass disposal and wound treatment to prevent infestations.

• Cochliomyia hominivoraxPrimary screwworm; distinguished by black fronto-orbital setae, limited extension of thoracic stripe, pigmented larval tracheal trunks, and presence of oral sclerite; attacks living tissue versus necrotic tissue
• Chrysomya rufifaciesHairy maggot blow fly; exotic species introduced to Americas that competes with C. macellaria and may reduce its abundance in some regions
• Chrysomya albicepsExotic calliphorid; larvae prey on C. macellaria larvae during dispersal; interspecific competitor
• Lucilia sericataCommon green bottle fly; used in maggot therapy; similar metallic coloration but different genus and larval morphology
• Phormia reginaBlack blow fly; forensic indicator with slower development rate than C. macellaria at equivalent temperatures

• blow fly
• carrion
• forensic entomology
• myiasis
• secondary screwworm
• livestock pest
• decomposer
• Calliphoridae
• screwworm
• medical entomology

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bohart Museum Features UC Davis Forensic Entomologist Bob Kimsey | Bug Squad
• Managing External Parasites of Texas Cattle - AgriLife Extension Entomology
• Why Forensic Entomologists Say Crime-Scene Investigators Should Carry Cans of Tuna
• They eat dead things, Part II - Blow flies, Calliphoridae — Bug of the Week
• Carp diem: Fish and blow flies, Calliphoridae — Bug of the Week
• How Entomologists Design the Diet for Mass-Reared Screwworm Flies
• Secondary Screwworm,Cochliomyia macellaria (Fabricius) (Insecta: Diptera: Calliphoridae)
• Abundance and seasonality of Cochliomyia macellaria (Diptera: Calliphoridae) in Southern Pantanal, Brazil
• Influence of Substrate Age on Oviposition Behavior of a Specialist Carrion Colonizer, Cochliomyia macellaria (Diptera: Calliphoridae)
• Physical and Physiological Factors Influence Behavioral Responses of Cochliomyia macellaria (Diptera: Calliphoridae) to Synthetic Attractants
• Life History of Cochliomyia macellaria (Fabricius, 1775) (Diptera, Calliphoridae), a Blowfly of Medical and Forensic Importance