Scarlet Lily Beetle

Lilioceris lilii — the scarlet lily beetle (also called the lily leaf beetle) — is one of the most striking small beetles in North America and one of about 130 species in genus Lilioceris (the lily leaf beetles — specialist herbivores of plants in family Liliaceae). The species is native to Eurasia (where it has been a familiar lily pest for centuries) and was accidentally introduced to North America — first detected in Quebec in 1992, then rapidly spread across Quebec, Ontario, and the northeastern US over the 1990s-2010s. The species is now established across most of northeastern NA and continues to spread south and west. Adults are 6-9 mm long, oval beetles with the species' diagnostic coloration: brilliant SCARLET-RED ELYTRA contrasted with BLACK HEAD, LEGS, AND ANTENNAE. The bright color combination is striking and immediately recognizable. The species is a major economic pest of GARDEN LILIES (Lilium and related Liliaceae genera) — adults and larvae feed exclusively on lily plants, defoliating leaves and damaging flower buds. NA gardeners growing lilies report that the species can completely defoliate established lily plants in a single season, with major damage to lily collections. The species was accidentally introduced via international plant nursery shipments and spread aggressively in the absence of native parasitoids that limit Eurasian populations. The species is famous for the LARVA'S REPULSIVE DEFENSIVE BEHAVIOR — one of the most-cited examples of inadvertent self-disguise in Coleoptera larvae. Larvae are bright orange-red with darker head capsules, but they cover themselves in their own MOIST FECAL EXCREMENT (forming a wet brown coating that completely covers the larva, hiding the bright color and creating a repulsive appearance that deters bird predators). The fecal shield is constantly produced and refreshed as the larva feeds — and it is so effective at deterring predators that bird and wasp predation rates on protected larvae are dramatically lower than on artificially-cleaned larvae in experimental studies. The fecal-shield behavior is shared with several other related lily-feeding beetle species (other Lilioceris species and members of the related Crioceris genus including the asparagus beetle) and is one of the most-cited examples of evolutionary convergence on excrement-based defense in herbivorous beetle larvae. Modern control approaches in NA gardens include: hand-picking adults and larvae (the bright red adults are easy to spot and capture), pesticide applications (with limited effectiveness due to lily flower aesthetic concerns), and BIOLOGICAL CONTROL with introduced parasitoid wasps from Europe (since 2010 — Tetrastichus setifer, Lemophagus errabundus, Diaparsis jucunda — have been imported and released in NA as classical biocontrol agents, with promising early results). The species is harmless to humans (no bite, no sting) but is a major nuisance for NA lily gardeners.