Regal Moth

History:

Also known referred to as the regal moth, royal walnut, and horn devil this is the only North American Saturniidae with this color scheme as well as size. The first time I ever saw this species was only 6 years ago. Regal moths are more of a southern species and their most northern range is just above the bottom of the state. Needless to say I had never found a caterpillar nor seen an adult of this species until I began to rear them. In the wild their density is far less than of other species. This species is wide ranging as far west as California and south to Florida. This species is bivoltine in most of its northern and western ranges and occasionally multivoltine in far southern ranges with adults on the wing 2-3 times a year. They appear to favor areas composed of mature hardwoods and semi mature forests.

Reproduction:

Adult moths lack functional mouthparts or digestive system and therefore they live only for about two weeks. This strategy seems odd as many other species of moths and butterflies feed throughout the period they are adults, but allow me to break down the evolutionary advantages that allow them to do this. The female moth emerges from a subterranean camber with fully developed ova which allows it to be ready to receive sperm from a male and begin depositing eggs the same night that it hatches. Male moths emerge with larger antennae that allow them to detect female pheromones up to a mile away. Males cover long distances flying in a zigzag pattern until pheromone particles have been detected. Females begin “calling” around 10:00 p.m. and continue till dawn. By releasing such effecting means of detection, females do not waste energy flying about seeking mates and reserve all their energy for seeking out host plants appropriate for their larva. Saturniidae regardless of species are by no means ever abundant in the environment. The ability of the males to detect females of the same species from long distances allow them to maintain populations under low density. Female moths frequently will deposit eggs onto the same host plant that they developed on to reduce their weight to allow them to fly away. Regal moth are the super flyers of the large silkmoths. Their wings are more narrow in shape and this allows for rapid, fast and long-distance flight.

Eggs:

large females are capable of laying up to 150-200 eggs, but the average is 100. Host plant specificity allows the developing larva to more efficiently convert the consumed biomass into fat reserves and tissue. This influences the size of the adult and the possible number of ova that females can carry. Stunted females can carry up to as few as thirty – fifty eggs. Eggs are deposited on the undersides of host leaves in loose groups of three – eight. The eggs can hatch in as little as nine days, or as long as 14 days depending on temperature. They are of decent size round in shape and yellow. Fertile eggs that are about to hatch being to progressively darken with the head capsule becoming prominently visible through the egg shell within the last few days of development. The Regal moth is polyphagous, but depending on their range are highly specialized on a specific host species. In general, Regal moth prefer and do best on Black walnut (Juglens nigra). Some other host plants I have observed larva feeding on are: persimmon, and sweet gum.

Larva:

Larva of this species emerge black on either end and yellow in the center. They are covered in tall spikey spines. They will consume all or part of the egg shell and soon after will begin to consume the leaves they find themselves upon. Larva of all saturniidae have 5 instars and disperse as soon as they hatch. Larva in their second instar lose the black on the ends and take on an overall brown look. The third instar larva are olive green with a wavy yellow mark running down each side and spiky brown spines along the sides and back. The fourth and fifth instar are bright green with yellow green accents along the seams of each segment and along the spiracles. Once they have reached the fifth instar they continue to consume leaves at an incredible rate until they are ready to pupate. Larva turn a turquoise color when they ae ready to pupate.

Cocoon:

Regal moth do not spin a cocoon but rather pupate in the ground.

Pupa:

The pupa of this species is long dark brown and with a sharp point at the end that looks like a barb. Unlike other species it is not as apparent how to sex them via antenna outlines on the pupal case. The way to sex them is to look at the pointed end and males will have a small pair of dots just above the barb. Females lack this mark.

Eclose:

The Regal moth emerge in late June to early July. To hatch it pushes its way through the ground using a screwing motion with the barbed end of its pupal case. It will then crawl across the leaf litter until it finds something to elevate itself to pump its wings and hang to dry. As nocturnal Saturniidae they wait till nightfall to take flight. Females reserve flight until they have been mated. It’s a general rule of thumb that if you capture a female at lights that she most likely has been mated and therefore eggs produced should be fertile.

Mortality factors:

Saturniidae larva are large and for most species defenseless. Birds readily seek out both the larva and adult moths. Moths drawn to night lights sit dazzled by the source where they are then picked off buildings once dawn emerges. Bats normally feed on small insects but will not pass up a large moth, leaving only wings as evidence. There are many parasitic fly and wasp species that utilize the larva as a host. Regalis and all North American Lepidoptera have taken heavy tolls due to the release of the tachinid fly used in attempt to control gypsy moth populations. Larva can experience high mortality rates due to fungal, bacterial, and viral infection. The larva in nature have no real capacity to combat high density issues and have adapted to leave gregarious habits by the 3rd instar. Pupa are consumed in the winter by hungry squirrels, mice, and woodpeckers who can easily rip through the silk. The Regal moth when disturbed during the day fall to the ground and flop about the ground. This strategy is intended to frighten off birds/predators and allow the moth to escape. It has been my general observation however that birds quickly learn that they are quite edible and ignore the erratic behavior. I’m assuming that normally in the wild birds happen upon these so infrequently that it most likely is an effective means to avoid predation.

Rearing notes:

The Regal moth is not hard to rear if they are given their own small container, however overwintering pupa and hatching them is another story. It is advisable to unearth the pupa and store them in barely damp sphagnum moss. Once it becomes warmer place them outdoors in a protected area with the pupa buried in a pot of sand and soil media. A cage should be placed on top of the pot so that the moths can climb right up the sides when they emerge.

Visit https://www.marylandbiodiversity.com/viewSpecies.php?species=336&showHidden=1  for more pictures of the larva and adult Regal moth.