Cochliomyia macellaria

(Fabricius, 1775)

secondary screwworm, secondary screwworm fly

Cochliomyia macellaria, the secondary , is a in the distributed throughout the Americas from southern Canada to Patagonia. The is a carrion colonizer whose feed on necrotic tissue, distinguishing it from the primary screwworm (C. hominivorax) which attacks living tissue. exhibit metallic green coloration with orange-red and . The species holds significant forensic importance for postmortem interval and has medical-veterinary relevance as a cause of secondary in livestock and humans.

Cochliomyia macellaria by no rights reserved, uploaded by Ken Kneidel. Used under a CC0 license.

Cochliomyia macellaria by (c) Katja Schulz, some rights reserved (CC BY), uploaded by Katja Schulz. Used under a CC-BY license.

Secondary Screwworm - Cochliomyia macellaria (33426797738) by Christina Butler from Georgia, United States. Used under a CC BY 2.0 license.

Pronunciation

How to pronounce Cochliomyia macellaria: //ˌkɒ.kli.ˈoʊ.mi.ə mæs.əˈlɛə.ri.ə//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

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

Images

Habitat

Associated with carrion and decomposing 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 odor 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.

Distribution

Americas from southern Canada through the United States, 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.

Seasonality

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

Diet

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

Host Associations

cattle - livestock for infest wounds and necrotic tissue; causes secondary cutaneous
humans - can cause in wounds

Life Cycle

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

Behavior

Females release 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 sites. Females commonly oviposit in with other females, leading to thousands of 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 8hour exposure time. No preference shown between previously colonized or uncolonized carcasses.

Ecological Role

carrion facilitating nutrient recycling and removal of carcasses and wastes. Serves as for other organisms including competing (Chrysomya albiceps larvae have been observed attacking C. macellaria larvae). Acts as for of (human ), contributing to economic losses in livestock. Important in for estimating postmortem intervals and determining time of .

Human Relevance

Forensic importance: most common on carrion in southern United States; used for postmortem interval in criminal investigations. Medicalveterinary importance: causes secondary in livestock and humans; poses economic risks to cattle industry through wound and transmission (carries Salmonella and swine influenza virus). potential: 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.

Similar Taxa

Cochliomyia hominivoraxPrimary ; distinguished by black frontoorbital , limited extension of thoracic stripe, pigmented larval tracheal trunks, and presence of oral ; attacks living tissue versus necrotic tissue
Chrysomya rufifaciesHairy ; to Americas that competes with C. macellaria and may reduce its abundance in some regions
Chrysomya albiceps ; on C. macellaria larvae during ; interspecific competitor
Lucilia sericataCommon green bottle ; used in ; similar metallic coloration but different and larval
Phormia reginaBlack ; forensic indicator with slower development rate than C. macellaria at equivalent temperatures