Cotinis mutabilis

Distinguished from the eastern green June beetle (Cotinis nitida) by geographic range—C. mutabilis occurs in the southwestern U.S. and Mexico, while C. nitida is eastern. C. mutabilis tends to have a duller, less iridescent green coloration and more variable markings. Separated from Japanese beetle (Popillia japonica) by much larger size (25-30 mm vs. 8-12 mm), lack of white abdominal tufts, and smooth rather than strongly striated elytra. Distinguished from emerald flower scarab (Euphoria fulgida) by larger size, more robust build, and less brilliant metallic coloration. The flight behavior—flying with elytra closed, resembling large bees—is characteristic of flower chafers including this species.

Adults are robust, oval-shaped beetles measuring approximately 25-30 mm in length. The body is predominantly metallic green to dull green with variable iridescence, sometimes with ochre or yellowish markings on the elytral margins. The elytra are smooth to faintly striated and often appear somewhat velvety or matte rather than highly polished. The underside is typically bright metallic green. Antennae are short with lamellate (plate-like) clubs. The hind wings are functional and deployed through a special elytral hinge characteristic of flower chafers, allowing flight with elytra remaining closed. Larvae are large, creamy white C-shaped grubs with a brown head capsule.

Primarily associated with riparian areas, urban and suburban gardens, orchards, and areas with fruiting trees. Adults are attracted to compost heaps, manure, and fermenting organic matter. Found in juniper/oak/pinyon woodland, mesquite/acacia thornscrub, and other warm, dry habitats with access to fruit resources. Larval habitat includes rich humus, decomposing organic matter, and compost.

Native to the southwestern United States (Arizona, California, Colorado, Nevada, New Mexico, Texas, Utah) and Mexico (widespread across most states including Aguascalientes, Campeche, Chiapas, Chihuahua, Coahuila, Colima, Durango, Guanajuato, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nayarit, Nuevo León, Oaxaca, Puebla, Querétaro, Quintana Roo, San Luis Potosí, Sinaloa, Sonora, Tlaxcala, Veracruz, Yucatán, Zacatecas). Also recorded from Central America: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua. Introduced or occasionally recorded in Florida.

Adults are active primarily from mid-summer (July) through fall, with peak activity in August and September in most of the range. In southern California and warmer areas, activity may begin earlier and extend longer. Adults are diurnal and crepuscular, often seen flying at dusk. Larvae are present year-round in soil and organic matter.

Adults feed on ripe and overripe fruits, especially figs, but also grapes, peaches, plums, and other soft fruits. They consume flower nectar and pollen, and are attracted to fermenting sap from tree wounds. They are not significant leaf feeders and do not skeletonize foliage. Larvae feed on decomposing organic matter, humus, and compost material; they are not root feeders and do not damage turf grasses.

• Ficus carica - foodPrimary common name source; adults feed on ripe figs
• Gutierrezia sarothrae - foodAdults observed feeding on flowers
• Dasylirion leiophyllum - noneNot associated; confusion with other scarabs possible

Complete metamorphosis. Eggs are laid in rich soil, compost, or decomposing organic matter. Larvae are large, C-shaped grubs that develop through three instars, feeding on decaying plant material. Pupation occurs in soil or compost. Adults emerge in summer, with a single generation per year in most of the range. Development time varies with temperature and food availability.

Adults are strong, agile fliers that can travel considerable distances. They are highly attracted to odors of ripe fruit, fermenting material, and manure. Adults often aggregate in large numbers on fruit trees, with groups of 60-70 individuals reported on single fig trees. They fly with a distinctive loud buzzing sound. When feeding on fruit, they may become sluggish and approachable. Adults are primarily diurnal but active into dusk. They are not known to exhibit defensive leg-spreading behavior like some scarabs.

Adults serve as pollinators when feeding on flowers. Their attraction to fermenting fruit contributes to nutrient cycling. Larvae are important decomposers, breaking down organic matter in compost and soil. The species provides food for birds, mammals, and insect predators. They are not considered significant agricultural pests despite occasional fruit damage, as they prefer overripe rather than marketable fruit.

Minor pest of ripe fruits in home gardens and orchards, though economic impact is limited due to preference for overripe fruit. Frequently used in educational outreach and citizen science programs due to large size, striking appearance, and ease of observation. Often mistaken for more damaging pests (Japanese beetle, green June beetle), leading to unnecessary concern. Captive specimens have been used successfully in educational demonstrations with children and students. Adults are attracted to compost and manure piles, which can be used for monitoring or collection.

• Cotinis nitidaEastern green June beetle; similar size and color but more iridescent, eastern U.S. distribution, more consistent yellow markings
• Popillia japonicaJapanese beetle; much smaller, with white abdominal tufts and strongly striated elytra, leaf skeletonizer behavior
• Euphoria fulgidaEmerald flower scarab; smaller, more brilliant metallic coloration, highly active and quick to fly, variable purple and turquoise color forms
• Cotinis texanaTexas flower scarab; similar range and habitat, smaller size, different elytral markings

Commonly misidentified as Japanese beetle due to green coloration, though much larger and behaviorally distinct. Often confused with eastern green June beetle (C. nitida) in name and appearance, but the two species are allopatric with different ranges. Despite common names implying significant pest status, adults prefer overripe fruit and are rarely damaging to marketable crops. Larvae are sometimes mistaken for pest scarab grubs, but they do not damage turf or plant roots.

• scarab beetle
• flower chafer
• southwestern US
• Mexico
• fig pest
• decomposer
• pollinator
• education
• misidentification

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Of Lady Beetles and Green Fruit Beetle Larvae | Bug Squad
• Bug Eric: What is, and is NOT, a Japanese Beetle
• How an International Education Program Fosters a Young Student's Interest in Entomology
• 2024 New Mexico Insect Collecting Trip iReport: Finale | Beetles In The Bush
• My response to “Can you talk to 10-year-olds about science?” | Beetles In The Bush