CASE STUDY: Saturniidae Moth Populations in Richmond, Rhode Island Part 1

When it comes to insects, butterflies and moths have always been my favorite type. Nothing beats a warm summer day sitting outside, watching butterflies visit your flowers. As much as I enjoy this though, it is the giant silk moths that fly at night that I am passionate about the most.

Newly hatched Callosamia promethea female.

Worldwide there are over 1,500 species of this amazing family of moths. Despite Rhode Island being such a small state, we do boast quite a few species ourselves, including the largest North American species, Hyalophora cecropia. According to the Bill Oehlke’s fantastic website, World’s Largest Saturniidae Site, sixteen species are known to live here. They are:

Actias luna (Luna Moth): flight time April to June (with possible 2nd brood)

Anisota senatoria (Orange-tipped Oakworm Moth) flight time June to July

Anisota stigma (Spiny Oakworm Moth) flight time June to August

Anisota virginiensis (Pink-striped Oakworm Moth) flight time June to July

Antheraea polyphemus (Polyphemus Moth) flight times April-May and July – August

Automeris io (Io Moth) flight time June to mid-August

Callosamia angulifera (Tulip-tree Silk Moth) flight time June to August

Callosamia promethea (Promethea Moth) flight time May to mid-August

Citheronia regalis (Regal Moth) flight time late June to mid-August

Citheronia sepulcralis (Pine Devil Moth) flight time mid-June to late July

Dryocampa rubicunda (Rosy Maple Moth) flight time May to August

Eacles imperialis (Imperial Moth) flight time July

Hemileuca lucina (New England Buck Moth) flight time September to October

Hemileuca maia (Buck Moth) flight time September to November

Hyalophora cecropia (Cecropia Moth) flight time May to early July

Samia cynthia (Cynthia Moth) flight time June to July

When we moved to Richmond, Rhode Island in 2019, I knew immediately I would love living here. We now live in a heavily wooded area with many prime Saturniidae caterpillar foodplant trees, including maples, oaks, cherries and sassafras. We arrived in the spring which left me little time to search for moths as we were unpacking and putting our home together. When things did start to slow down though, I tried using moth lights. I did manage to attract some nice sphinx moths, but other than nightly visits by Dryocampa rubicanda, there was no evidence of Saturniidae. It was a bit discouraging but I did know it was too late in the season for the spring brood. The only other evidence of these amazing moths for that season was a cecropia caterpillar found that had been run over by a car crossing the road.

Luna moth attracted to my moth light (5/22/2020).

Things took an upswing in 2020. Despite the coronavirus, the moth situation improved. I was able to attract Actias luna on three separate occasions to my lights, which for me was amazing. Rubicanda was also in abundance. My landlord, who lives next door, also sent me a picture of an Antheraea polyphemus that she found at her house as well. This was very exciting to me as it now confirmed four species. My next thought was to figure out if the other twelve species could be found and how their local populations were. I had three thoughts on how to do this. Continue using moth lights and see what came. Find caterpillars and cocoons in the wild. Use gravid females to attract males. The last method seemed the best to help with my goals.

Polyphemus moth found by my landlord (7/5/2020).

The new plan began to take place in the spring of 2021. First off I did the research on the flight times for all moths in question. This data would let me know when to expect to find these species, either by attraction to light or from scenting females attracting males. This would also tell me approximately when cocoons would hatch.

While out walking on the road I live on, I was able to find a cecropia cocoon as well as a Callosamia promethea cocoon, confirming species number five. Then, a few days later on April 19, my girlfriend also found a cecropia cocoon while out walking. The fact that we were finding these cocoons, right on the edge of the road, encouraged me to venture out more. I checked some local hiking trails and found a pattern. Though I would not find any cocoons on the trails themselves, I almost always found cocoons on the side of the road on either side of the trail. Previously hatched promethea was the most abundant. All were found on cherry trees except one, that was on a sassafras. In many instances multiple cocoons could be found on a single tree.

In addition to the handful of cocoons we found, I was able to obtain some others from friends (cecropia, polyphemus, luna, cynthia and regalis). Though I was doubtful that I would attract cynthia and regalis, I felt my chances were better living on the border of Connecticut. Cynthia has not been seen in Rhode Island for quite some time to my knowlege. I am guessing this is due to the removal of Ailanthus, its primary caterpillar food plant, in the Providence area. Also, I thought that the last Rhode Island record for regalis was in 1939, but further research revealed that a gravid female was found in 2017 in Tiverton, Rhode Island. Thank you to David Gregg for this information!

According to the book “The Wild Silk Moths of North America,” Samia cynthia was introduced into the United States in the late 1800s from Asia for silk production. Though attempts at silk collecting failed, this moth became established as a result of escapees and intentional releases. Though I know of no confirmed reports of this moth being here, I have heard stories that in Providence, where Tree of Heaven (Ailanthus altissima) was quite abundant, this moth could be found. The story went that cocoons could be found in great numbers, resembling ornaments on a Christmas tree, on the foodplant. I definitely need to do more research on this species.

Samia cynthia, hatched on April 21, 2021.

So my plan was in place. I had plenty of cocoons on hand. Being April in Rhode Island, the weather would change almost daily. This season we have gone from 70 degree days to days with snow. I am sure these deviations wreak havoc with nature. Since the majority of flight paths start in May, it now became a waiting game. One nice female cynthia did end up hatching on one of the 70 degree days unfortunately.

Polyphemus, luna and cecropia cocoons.

The next step was creating a Facebook group called Rhode Island Saturniids. The hope here was that Rhode Islanders would post pictures with locality and date of giant moths that they encountered. This would then create a detailed database on these moths in Rhode Island.

Look for part two of this series in May!

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