Lily Leaf Beetle

The scarlet lily beetle belongs to the order Coleoptera, and the family Chrysomelidae, the leaf beetles. The adult lily beetle is about 6 to 9 mm (1⁄4 to 3⁄8 in) in length, with relatively long legs and antennae. Its elytra (harder forewings) are bright scarlet and shiny. Its underside, legs, eyes, antennae and head are all black. It has large eyes, a slim thorax, and a wide abdomen. Each antenna is made up of 11 segments. The eyes are notched and there are two grooves on the thorax. The scarlet lily beetle may be confused with the cardinal beetle (Pyrochroa serraticornis), which also has red elytra and a black underside. The wing cases of the lily leaf beetle are dimpled and are shinier and more rounded than those of the cardinal beetle, which are relatively dull, and narrower, flatter, and more elongated. The cardinal beetle also has comb-like antennae. The lily leaf beetle is herbivorous, while the cardinal beetle preys on insects. The lily leaf beetle is also confused with unspotted ladybirds, but it is narrower in shape.

The lily leaf beetle is indigenous to parts of Europe and Asia. It is thought to have been introduced to North America through the importation of plant bulbs in 1943. First spotted in Montreal, it spread throughout Canada and appeared in Massachusetts in 1992, and by 2012 was in all six New England States, as well as New York and Washington states. In Canada it is found from the Maritime Provinces west to Manitoba. As of 2001, it had spread as far west as Alberta, and as of 2017 full infestations had been reported as far north as the Edmonton, Alberta area. It has also become established as an invasive species in the United Kingdom since being first recorded in 1839, although the first colony did not become established until 1939 and it did not spread far until the 1980s, then more rapidly from the 1980s onwards. Since then it has spread from Surrey in southern England as far north as Inverness, Scotland. It is also found in Ireland, the Middle East and North Africa.

The beetle overwinters in the soil and emerges early in spring. The adult is generally found in moist, cool environments. It emerges in spring to feed and mate. The female can lay up to 450 eggs each season in batches of about 12 on the undersides of leaves. It arranges the red-orange to brown eggs in narrow irregular lines along the midrib, where they are more concealed. The eggs then hatch into yellow, brown or orange larvae in about 1–2 weeks. The larvae feed for up to 24 days, beginning underneath the leaf then working up the rest of the plant, and cause the most damage. Their preferred feeding locale is underneath the leaf or at the node where the leaf meets the stem. They then burrow in the ground to pupate in a cocoon of soil bound with saliva. In about 20 days they emerge as adults and continue to feed until winter. More than one cycle can occur in one year.