The Carlisle Mosquito Online

Friday, March 31, 2006


(Photos by Kay Fairweather)

Biodiversity Corner Diurnal firefly

Signs of spring are all around and none more telling than the emergence of the diurnal fireflies. This year I noticed them for the first time on March 7 and they are out again now. I see them mostly on the bark of maple trees and occasionally find one on the side of the house or on the doorstep.

Name: The common diurnal firefly is Ellychnia corrusca. It is a member of the Lampyridae family, also known as the lightning bug family or firefly family which is altogether too bad since they are neither bugs nor flies — they are beetles (order Coleoptera). The Ellychnia genus is the black sheep branch of the firefly family — they have no lights. Being diurnal, they don't need them. They have been put in the same family as the fly-by-night fireflies with lights (genus Photinus) because they share other common physical characteristics. Mitochondrial analysis confirms the close relationship and suggests that the divergence is relatively recent.

Some beetle nomenclature: Beetles have three parts to the thorax; the first part is the most distinct and is called the prothorax. It is covered by a plate called the pronotum which is so large and prominent that it can appear to be the entire thorax. Most beetles have two sets of wings. The front pair are called elytra. They are usually hard; they cover the membranous flying wings, and they don't overlap — they touch each other forming a straight line down the center of the abdomen.

Identifying characteristics: The diurnal firefly is mostly black but has pink-red stripes on the pronotum and fainter pink-red lines on the elytra. When at rest, the head is tucked in under the pronotum so it looks as if the antennae are coming from the thorax. There are four Ellychnia species.
If the elytra are at least six millimeters long, you can be reasonably sure you have a member of the Ellychnia corrusca complex. The ones on my maple are fairly uniform in size with elytra about 10 mm. When you pick them up, they extend their little heads beyond the pronotum, and wave their antennae. You can see that the underside of the thorax is pink.

Life cycle: Diurnal fireflies spend the winter in grooves in the bark of trees, as adults. They become active in March. They mate during April and early May and die by June. The eggs hatch into larvae in about 16 days. New generation adults are seen in August

Food chain: The adults are fluid feeders. They feed on maple sap and Norway maple nectar in the spring, and aster and goldenrod in the fall. If you tap for sap on the maples, you may find diurnal fireflies that have drowned in the bucket. The fireflies use nasty-tasting chemical deterrents to protect themselves from predation.

References: Richard E. White, Peterson Field Guide to Beetles; Rooney and Lewis, Life History and Mating Behavior of Ellychnia corrusca.

2006 The Carlisle Mosquito