Caterpillars on Distant Hill
A Southern Species Moving North
The Giant Swallowtail (Papilio cresphontes) is the largest butterfly in Canada and the United States. Adults have a forewing span of 4 to almost 6 inches (avg. 5.5 inches) for males and a span of 5 to 7 inches (avg. 5.8 inches) for females. It is an uncommon stray in southern New Hampshire and Vermont, but we have had them here at Distant Hill Gardens for the past two years.
Is their presence in New England an example of climate change at work?
A paper published last year in Nature Climate Change seems to support that theory. They reported that many of the southern butterfly species in the US are packing up and moving north... "Our results suggest that a major, climate-induced shift of North American butterflies, characterized by northward expansions of warm-adapted and retreat of cold-adapted species, is underway."
The caterpillar of the Giant Swallowtail is as least as interesting as the butterfly. It looks exactly like a bird dropping, making it unappetizing to most insect-eaters. If it does happen to be threatened by a predator, a bright red, forked structure called an osmeterium emerges from its head, along with releasing a strong noxious odor.
The caterpillar has the nickname 'Orange Dog' due to preference for plants in the citrus family. It is very common in Florida and is considered a pest in the citrus groves throughout the State.
Here in northern New England, it will feed on Common Prickly Ash (Zanthoxylum americanum) or the Common Hop Tree (Ptelea trifoliata), if available. Both are native plants in the citrus family. Only the Prickly Ash can be found in this part of New Hampshire.
The only plant growing at Distant Hill Gardens that we have found Giant Swallowtail caterpillars feeding on is a Gas Plant (Dictamnus albus). It turns out that Dictamnus albus is in the same botanical family as
There is one other plant in the Rue family growing at Distant Hill Gardens, an Amur Corktree (Phellodendron amurense). We will have to keep an eye out for the Giant Swallowtail caterpillar feeding on its leaves.
Change is Good
- Simple metamorphosis: Grasshoppers, along with dragonflies and many other insects, go through simple metamorphosis. This is a 3 stage process: Egg to Nymph to Adult. The young nymphs usually look much like small wingless adults. The wings develop externally.
Here is a partial list of insects that use simple metamorphosis.
A Band-winged grasshopper in the Nymph stage of development. Note the short stubby wings.
A Band-winged grasshopper, in the Adult stage of its development. Note the long wings.
- Complex metamorphosis: Butterflies and moths undergo complex metamorphosis, in which there are 4 distinct stages: Egg to Larva to Pupa to Adult. With Complex metamorphosis, the immature insects and the adults have different forms, often live in different habitats, and may have very different behavior.
A Monarch caterpillar, the Larva stage of complex metamorphosis.
A Monarch chrysalis, the Pupa stage of complex metamorphosis.
A Monarch Butterfly, the Adult stage of complex metamorphosis.
Long Hairs on the Hill
Tussock moths Caterpillars are all members of the insect family Lymantriidae . The common name is derived from the hair tufts, or tussocks, found on most larval forms. The large larvae, or caterpillars, are hairy with many species having stinging hairs. Most feed on foliage of trees and shrubs. Some Lymantriidae caterpillars, such as the Gypsy Moth, are considered major forest pests. There are about 350 known genera and over 2,500 known species of Tussock Moths found all over the world, in every continent except Antarctica.
Notable Tussock Moth Species and Genera
- Brown-tail, Euproctis chrysorrhoea
- Yellow-tail, Euproctis similis
- Gypsy moth, Lymantria dispar
- Nun Moth, Lymantria monacha
- Pale tussock moth, Calliteara pudibunda
- Pine tussock moth, Dasychira plagiata
- Arctic woollybear moth, Gynaephora groenlandica
- Rusty tussock moth or Vapourer, Orgyia antiqua
- Western tussock moth, Orgyia vetusta
- White-marked tussock moth, Orgyia leucostigma
- Douglas-fir tussock moth, Orgyia pseudostugata
- Satin moth, Leucoma salicis
- Coca moth, Eloria noyesi
- Painted apple moth, Teia anartoides
This is a photo of a tobacco hornworm, the caterpillar of a Carolina sphinx moth (Manduca sexta) feeding on a tomato plant at Distant Hill Gardens. The tobacco hornworm, is closely related to, and often confused with, the very similar tomato hornworm. Both feed on plants in the Nighshade Family. The tomato hornworm is the caterpillar of the five-spotted hawk moth (Manduca quinquemaculata).
Note the Red horn at the tail end of the caterpillar, and the seven diagonal lines on its side. These identify this as a tobacco hornworm. The tomato hornworm has a Black horn, and eight V-shaped markings in place of the diagonal lines.
This is the same tobacco hornworm seven days later. It is covered with cocoons of Cotesia congregata, a species of parasitic braconid wasp. They lay eggs in the bodies of tobacco hornworms. The eggs hatch inside the hornworm and the larva feed internally, later to emerge from the body to spin their cocoons.
If you find a hornworm with these white cocoons, just let it be. Young wasps will soon emerge from the cocoons and lay their eggs in other unsuspecting tobacco hornworms.
Note: The insect on the body of the hornworm is not a braconid wasp. I'm working on getting a positive ID. Do you know what the insect is?
Mowed For The Monarchs
Monarchs butterflies need milkweed to survive. The caterpillars feed on the leaves, which makes them unpalatable to birds. The sap contains cardiac glycosides, which are toxic to birds.
We favor the milkweed in our fields and go out of our way to help it thrive. We have found that mowing in mid May, just as the milkweed plants are emerging, works best. It develops a healthy crop for the Monarch butterflies by cutting the already tall grasses. The milkweed isn't cut, which allows it to become the dominant plant in the field. We mow a second time in late October, after the plants have gone to seed.
Tagging Monarch Butterflies
Working with ‘Monarch Watch’ in 2003, Michael tagged a butterfly that was found six months later in El Rosario, Mexico, part of the Monarch Butterfly Biosphere Reserve. This is the area where the majority of the Monarchs east of the Rocky Mountains migrate to for the winter; an estimated 60 million to 1 billion butterflies every year. That small butterfly from New Hampshire had flown 2288 miles!
I Can’t Make Heads or Tails of It
The Banded Woolly Bear Caterpillar is found in temperate regions of North America. It emerges from the egg in the fall and overwinters in its caterpillar form, when it literally freezes solid. It survives being frozen by producing a cryoprotectant in its tissues. Because the summer period for vegetative growth and hence feeding is so short in some northern areas, the Woolly Bear can feed for several summers, freezing again each winter before finally pupating. Some are known to live through as many as 14 winters in the Arctic. Once it emerges from its pupa as an Isabella Tiger Moth it has only days to find a mate before it dies.
Folklore About the Banded Woolly Bear Caterpillar
Folklore of the eastern United States and Canada holds that the relative amounts of rust and black on a Woolly Bear caterpillar are an indication of the severity of the coming winter. It is believed that the narrower the rust colored band in the middle of the Woolly Bear caterpillar is in the fall, the more severe the winter will be. In reality, hatchlings from the same clutch of eggs can display considerable variation in their color distribution, and the rusty band tends to change width with age.