Polyphylla occidentalis

Males are readily identified by their conspicuously enlarged, lamellate antennae that can be held splayed open; these are substantially larger than the antennae of females and most other scarab beetles. The ten white longitudinal stripes on the brownish elytra separate it from unstriped or differently patterned scarabs. It is larger than most Phyllophaga (May beetles) with which it may co-occur. Similar Polyphylla species may require examination of subtle differences in striping pattern, body proportions, and male genitalia for definitive identification. The species is most reliably distinguished from P. decemlineata (ten-lined June beetle) and other congenerics by geographic distribution and minor morphological differences in elytral sculpture and stripe pattern.

Adults are associated with pine forests and adjacent open areas. The species has been documented in sand dune habitats in some regions, though it appears less specialized for sand habitats than some other Polyphylla species. Adults are frequently attracted to lights at night, suggesting they move between forested breeding areas and more open foraging or mating sites. The subterranean larvae develop in soils beneath host plants.

Southeastern United States, with records from Alabama, Florida, Georgia, Maryland, Mississippi, North Carolina, South Carolina, and Virginia. The species is widespread within this range and is the eastern counterpart to the western P. decemlineata.

Adults are active throughout the warm summer months, with peak activity during June and July. Males are attracted to lights after dusk and cease activity several hours after sunset. The species has an annual life cycle with one generation per year.

Adults feed on pine foliage, particularly needles of Pinus species. Larvae consume roots of sedges (Cyperaceae) and likely other herbaceous plants.

• Pinus - adult food plantAdults feed on pine needles
• Cyperaceae - larval food plantLarvae feed on sedge roots

Complete metamorphosis with one generation annually. Eggs are laid in soil. Larvae develop underground, passing through three instars while feeding on roots. Pupation occurs in soil cells. Adults emerge in early to mid-summer. The duration of larval development and specific timing of pupation have not been precisely documented for this species.

Males are strongly attracted to artificial lights at night, where they fly with a loud, buzzing sound and frequently collide with surfaces. At lights, males hold their antennae splayed open to detect female sex pheromones. Females are flightless or rarely fly, remaining near the ground where they release pheromones to attract males. Males engage in rapid, irregular flight several meters above ground during late afternoon, transitioning to slower, purposeful upwind flight with zigzag returns at dusk—behavior indicative of osmoclinotactic orientation toward pheromone sources. Mating occurs on the ground after males locate stationary females. Multiple males may be attracted to a single female. Adults stridulate when handled, producing an audible sound.

As a root-feeding larva, the species contributes to soil nutrient cycling and aeration. Adults function as folivores on pines, with limited impact on tree health at typical population densities. The species serves as prey for various vertebrate and invertebrate predators. The specialized mate-finding system, with flightless females and pheromone-tracking males, represents an interesting case of sexual dimorphism in dispersal and reproductive behavior.

Adults are occasionally nuisance pests at lights during summer evenings. The species has no significant economic impact on agriculture or forestry. It is of interest to entomologists and naturalists due to its distinctive appearance and behavior. The loud buzzing flight of males makes them conspicuous and sometimes startling to observers.

• Polyphylla decemlineataThe ten-lined June beetle is morphologically very similar, with nearly identical striping pattern and male antennae structure. It is distinguished primarily by western North American distribution (west of the Great Plains versus southeastern U.S. for P. occidentalis) and subtle differences in body proportions and elytral sculpture.
• Phyllophaga spp.May beetles are similar in general scarab form and nocturnal, light-attracted behavior, but are generally smaller, lack the distinct ten-striped elytral pattern, and have less dramatically enlarged male antennae.
• Polyphylla hammondiHammond's lined June beetle is larger (often exceeding 30 mm), with a more robust body and different geographic distribution (Great Plains sand dunes). It is more strictly associated with sand dune habitats than P. occidentalis.

• scarab beetle
• June beetle
• pine feeder
• sexual dimorphism
• pheromone communication
• flightless female
• nocturnal
• light-attracted
• southeastern United States

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