"FEN" BUCK MOTH
Hemileuca maia sp.

by Tony McBride at tmcbride@nac.net

male "fen" buckmoth

This "species" is a complex of wetland buckmoths which occurs throughout the Great Lakes region with isolated populations in nearby states, including New Jersey. In New Jersey, these moths occupy calcareous fens - relatively small, wet sedge meadows with alkaline, limestone-rich soils. These moths can only be found in six such fens in extreme northern New Jersey.

According to The Wild Silkmoths of North America by Tuskes, Tuttle, and Collins, these buckmoths (Great Lakes Complex), can exhibit a wide range of variation and are probably more closely related to H. nevadensis than to H. maia. In fact, New Jersey fen individuals tend to have wider white forewing bands than the nominate maia which inhabit scrub oak thickets on nearby ridgetops. Adults fly from late September to mid October with a peak about October 1st. They are most active during a period from 10:00 A.M. to 3:00 P.M.

The females, which are larger and lighter in color than the males, release a pheromone from the tip of the abdomen to attract a cloud of males, one of which flies in to mate with each female. The gravid female then lays one or more egg rings, in typical buckmoth style, on stems of the foodplants. The eggs overwinter.

Males also differ from females in that they have a bright red tip to the abdomen. Only the ovipositor (visible during "calling" or egg deposition) of the female is reddish in color.

Female moth (right) ovipositing on willow.

In New Jersey, larvae feed on several wetland plants, including shrubby cinquefoil (Potentilla fruticosa), Dwarf Birch (Betula pumila), and various willows (Salix spp).

Early instar larvae are gregarious and form "globs" on one of these plants. Later instar larvae are wandering, solitary feeders and will switch to other foodplants at this time.

Larvae in New Jersey are typically ready to pupate by mid July. Pupae are formed among leaf litter just above the surface of the ground.

Early instar larvae (right) on Dwarf Birch

Late instar larvae are impressive, with urticating spines and bright coloration. The dorsal spine clusters are orange, while those on the sides are black.

Larvae at most New Jersey sites have a yellow band of moderate intensity on the sides.

Mature larva (left) on willow.

These moths can be superabundant in their limited fen habitat. I have seen as many as thirty-five males flying at one time. These fens are often surrounded by mature deciduous forest and the moths turn back into the fen as soon as they reach the edge. They will not fly into the surrounding woodlands. Males have a patrolling style flight which takes them on transects across the fen. Females have a bobbing flight where they will rise a few feet and then drop, as if trying to locate a site to lay their eggs.

--------- "fen" buckmoth habitat -------------------- male ventral surface

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