{"id":16268,"date":"2025-06-11T11:01:02","date_gmt":"2025-06-11T16:01:02","guid":{"rendered":"https:\/\/uwm.edu\/field-station\/?p=16268"},"modified":"2025-06-11T11:03:15","modified_gmt":"2025-06-11T16:03:15","slug":"giant-silk-moths-again","status":"publish","type":"post","link":"https:\/\/uwm.edu\/field-station\/bug-of-the-week\/giant-silk-moths-again\/","title":{"rendered":"Giant Silk Moths Again"},"content":{"rendered":"\n

Salutations, BugFans,<\/p>\n\n\n\n

2025<\/strong>\u00a0\u2013 The BugLady confesses that she rarely finds these Giant silk moths, either as adults or as caterpillars.\u00a0So rarely that some of these pictures are scanned slides\/transparencies, from the olden days.\u00a0In the years since this episode was posted, she has written about another Silk moth, the Imperial moth<\/a>\u00a0(which BugFan Mary found for her).\u00a0<\/p>\n\n\n\n

2014 –\u00a0<\/strong>When the BugLady was in high school, a friend found an ovipositing Cecropia moth and gave her a twig with 9 pale eggs on it.\u00a0The eggs hatched into tiny, black fuzzy caterpillars, and the BugLady kept their cage – a seven-inch-wide cylinder of window screen fastened to a block of wood and topped by more screen (it doesn\u2019t have to be fancy) – full of food and empty of frass (a reasonable housekeeping philosophy, overall) and they grew and prospered.\u00a0After a while she noticed that although food was not a limiting factor and escape was unlikely, the nose-count was, one-by-one, decreasing, and in the absence of actual carcasses, she suspected that they were cannibalizing each other.\u00a0Ultimately, a single caterpillar remained, and it spun a cocoon.<\/p>\n\n\n\n

\"Green<\/figure>\n\n\n\n

Cecropia, Promethea, Polyphemus and Luna moths are members of the Giant Silk Moth family, Saturniidae, and some are giants indeed, with wingspreads measuring 4\u201d to 6\u201d (there are classic Greek myths behind those names, and Saturnia, too, so dust off your old Edith Hamilton mythology book from freshman English and look \u2018em up.).\u00a0There are smaller members of the family, including the Buck moth, of previous BOTW fame\u00a0Buck Moth (Family Saturniidae) \u2013 Field Station<\/a><\/a>.\u00a0<\/p>\n\n\n\n

Saturniids are\u00a0distantly<\/em>\u00a0related to the Oriental moth that is used in silk production; some Asian and South American Saturnids are semi-domesticated and the silk spun by their larvae is harvested.\u00a0North American silk moths aren\u2019t used to make silk, although the BugLady has read that cocoons have been unraveled by people desperate for leaders for fishing line.\u00a0The highly successful, invasive gypsy moth, in the tussock moth family, was originally imported to test its feasibility as a silk producer (what could possibly go wrong?).<\/p>\n\n\n\n

The old Lepidopterists\u2019 adage that \u201cThe more homely the caterpillar, the more spectacular the adult\u201d does not apply to the Saturnids, remarkable moths with remarkable offspring.\u00a0Northern species tend to have a single brood per year, while their Southern brethren may have two or three.\u00a0Wherever they are, Saturnids overwinter as pupae in a state of\u00a0diapause<\/em>\u00a0or suspended animation \u2013 they pupate in fall but their transformation into adults doesn\u2019t begin until spring.\u00a0The caterpillars are large\/huge \u2013 up to four inches long – and often have spiny tubercles, (which, except for the Io moth caterpillar, are harmless to the touch).\u00a0Luna and Polyphemus caterpillars can make a clicking sound with their mouthparts to warn predators, and if that doesn\u2019t do the trick, the next step is regurgitation of a nasty substance.\u00a0Saturniid caterpillars feed on the leaves of a wide variety of trees and shrubs, and a few are serious defoliators.<\/p>\n\n\n\n

\"Male<\/figure>\n\n\n\n

Saturnids typically fly at night.\u00a0The fancy antennae sported by Saturnid males<\/a>\u00a0allow them to detect \u201ccome hither<\/em>\u201d pheromone signals emitted by the females.\u00a0He can zero in on her from more than three miles away, his antennal receptors picking up her \u201cperfume\u201d even when it has diffused to only a few molecules, and following it into the higher concentrations where she is.\u00a0Giant silk moths, having no gut and only vestigial mouthparts, live to reproduce, and the lipids that they store as caterpillars nourish them as adults.\u00a0Adults are fed upon by Screech Owls and bats; caterpillars have a number of parasites; and woodpeckers extract pupae from their cases.\u00a0Some species, especially the Luna and Cecropia moths, are parasitized by alien tachinid flies (of previous BOTW fame) that were imported to control gypsy moths but found the slow-moving Saturniid caterpillars easier prey.\u00a0<\/p>\n\n\n\n

A CECROPIA caterpillar (Hyalophora<\/em>\u00a0cecropia<\/em>) that starts off tiny, black and bristly, progresses to small, yellow and bristly, and ends up as an astonishing, pale green creature that\u2019s the size of your thumb and decorated with non-toxic, Technicolor knobs (though the caterpillar itself contains both a toxin and an antibiotic).\u00a0A startled Cecropia caterpillar may thrash about, releasing droplets of its poisonous \u201cblood,\u201d which may cause topical irritation and a runny nose and eyes in its victim.\u00a0It eats a wide variety of tree leaves including box elder, ash, apple, maple, willow, poplar and dogwood (the BugLady fed hers lilac and has photographed them on willow and box elder).\u00a0<\/p>\n\n\n\n

\"Gray,<\/figure>\n\n\n\n

Its gray, spindle-shaped cocoon is spun on along a branch or at the base of a tree trunk.\u00a0Several layers of tough silk, with air spaces in between, insulate the pupa from abrupt temperature changes during its transformation, and small birds and mammals might feed on it during winter.\u00a0A researcher in the Southeast distinguished between silken cocoons that were \u201cbaggy\u201d and those that were taut, the author noting that the spinners of baggy cocoons were better at enduring prairie burns and surviving to emerge as adults.\u00a0<\/p>\n\n\n\n

With wingspans of four to six inches and more, Cecropias are the largest moth in North America. They are found east of the Rockies and north of the Rio Grande in open areas with the caterpillar host plants nearby.\u00a0There can be some regional differences in appearance, and the Cecropia hybridizes with the Columbia moth in part of its range.\u00a0Sexual dimorphism exists in both adults and pupae, where females may be larger.<\/p>\n\n\n\n

POLYPHEMUS MOTHS (Antheraea polyphemus<\/em>) are found in woodlands, urban\/suburban areas and wetlands throughout North America. They are slightly smaller than Cecropias and relatively unmarked, but in honor of the one-eyed Cyclops (see Edith Hamilton), they have a single eyespot in each hind wing. When alarmed, they flick their wings to expose the eyes more dramatically.\u00a0In the picture of the happy couple, the male is on the left (check out his antennae); the female, her body large to accommodate all her eggs, is on the right.\u00a0<\/p>\n\n\n\n

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\"Polyphemus<\/figure>\n\n\n\n
\"Pair<\/figure>\n\n\n\n
\"Green<\/figure>\n<\/div>\n\n\n\n

The caterpillars eat the leaves of apples, cherries, oak, maple, grape, willow and more. They hide the evidence of their meal by severing the leaf\u2019s petiole after feeding on it \u2013 no half-chewed leaf to attract the eye of a predator. According to Wikipedia, a caterpillar consumes 86,000 times its original weight in leaves during the two months between hatching and pupation! Its cocoon incorporates a leaf of their host tree, sometimes attached solidly to a twig, and sometimes dangling<\/a>\u00a0and eventually falling to the ground to rest in the leaf litter. Squirrels can be serious predators of Polyphemus caterpillars.\u00a0<\/p>\n\n\n\n

\"Promethea<\/figure>\n\n\n\n

PROMETHEA MOTHS (Callosamia<\/em>\u00a0promethea<\/em><\/a>) are found in woodlands from the Atlantic to the Great Plains. The caterpillars bear a family resemblance to Cecropias (but lack the row of paired, plain yellow knobs) and also eat lilac and forest trees like ash, cherry, basswood, birch and maple, although populations may become food specialists, regionally. When it\u2019s time to pupate, Promethea caterpillars reinforce the attachment of a leaf to its host plant, fold the leaf around themselves and then spin a cocoon inside. The \u201cinside-the-leaf\u201d part is a good camouflage strategy; the \u201clast-leaf-left-on-the-tree\u201d part, not so much.\u00a0<\/p>\n\n\n\n

Adult male and female Promethea moths exhibit strong sexual dimorphism \u2013 the male is dark brown<\/a>, and the female is reddish and can be mistaken for a small Cecropia<\/a>. \u00a0<\/p>\n\n\n\n

\"Adult<\/figure>\n\n\n\n

The LUNA MOTH (Actias luna<\/em>) lives in North America, east of the Great Plains. What an improbable moth for our less-than-tropical landscape! It has swallowtails, a wingspan of 4 \u00bd\u201d and a small, transparent eyespot.\u00a0Bugguide.net\u00a0says that the color of the wing borders depends on geography – the first brood in the South is edged with brown or pink, while subsequent Southern broods and the single Northern brood have yellow edges, but this adult was photographed in Ozaukee County, WI.\u00a0Go figure.<\/p>\n\n\n\n

\"Bright<\/figure>\n\n\n\n

The bizarre reddish caterpillar in the netting is the normally-chartreuse caterpillar<\/a>\u00a0of the exquisite Luna Moth.\u00a0It was captured halfway between the hickory tree whose leaves it probably nibbled (they like birch, alder, and sumac, too), and a thicket where it intended to pupate.\u00a0Some caterpillars undergo a color change when they have finished eating and are about to pupate; this one had a death-grip on the netting and was minutes away from pupating.\u00a0The cocoon is constructed in the leaves of the trees and is designed to fall into the leaf litter when the tree loses its leaves<\/a>.<\/p>\n\n\n\n

Edith Hamilton has something to say about Prometheus and Luna, too.<\/p>\n\n\n\n

Caterpillars and cocoons, especially those of the Giant Silk moths, are dynamite tools for teaching kids about Nature, but the landlord (you) has certain responsibilities: <\/p>\n\n\n\n