The Giant Swallowtail (Heraclides cresphontes sometimes known as Papilio cresphontes) is a truly spectacular butterfly in the Parnassian (Papilionidae) family of butterflies. The Giant Swallowtail (name shortened to GST) is generally found from May through September in many parts of the United States but flutters about year-round in Florida and in the south. The upper-side is dark with a yellow chevron and the under-side is the yellow that just can't be described. It is a fairly large butterfly whose wingspan can reach from 4" to 6.25" and when you see one, you won't likely forget it!

The Giant Swallowtail will oviposit (lay eggs) on trees and herbs in the citrus (Rutaceae) family such as Navel orange, Rue (Ruta graveolens), and Meyer's lemon; and Hop tree (Ptelea trifoliata). The female will often look for a young leaf and will oviposit single eggs on the top of the leaf. Keep in mind, that this is not always the case as I have found eggs on older leaves and even on the undersides of a few...

Like other swallowtail eggs, the Giant Swallowtail’s is spherical. Colour can be sort of yellow to greenish, depending upon the light. After four to seven days, a teeny little caterpillar hatches.

It will begin by poking its little head out and slowly wriggling out into the world.

*Scroll to the bottom of this page to  see a little Giant Swallowtail hatch!

The 1st instar hatchling is a brownish colour with goldish little protuberances. The first thing it will do is turn around and eat its eggshell (the chorion) before going off to eat the leaves of the host plant.

Even within minutes of its ‘birth’ the little one will show its ‘temper’ (for lack of a better word) and can try to scare off any potential predators by  poking out its osmeterium, a fleshy horn-like membrane that gives off a noxious odour that is meant to deter a predator.

In this picture on the right, if you look carefully, you can see its ‘scary’ posturing! The osmeterium is that horned looking apparatus at the top of the larva’s head.

The first instar are very cute. They are also more apt to die in the first few days so if you do raise this particular species, be very careful and do not handle them at this particular stage if at all possible. Instead, let them just be…

Here’s a good ‘profile’ of the little baby…cutie-patootie, right?

Now, check out big brother (or maybe sister?).

This 2nd instar, crawling about on a Rue stem, ate ‘baby’ for lunch just yesterday! Euuw! Yep, like many swallowtails, Heraclides cresphontes are cannibalistic so it is best to raise them separated, if at all possible, particularly if you have different ‘sized’ larvae. Don’t assume that just because two caterpillars hatched at the same time that they should be okay…

Note: Some will say that the caterpillar doesn’t notice the other caterpillar…I think the big guy just thinks, “Hmmm...more protein for me!” tee-hee-he

As the Giant Swallowtail larva matures, it changes colour; going from light brown to a very dark chocolate brown. If you were to come across one it resembles bird poop which is a great form of camouflage for the caterpillars as it helps to keep birds and other predators from eating them. If you were to pick up or touch one you’d be surprised to find that they they feel much like a candy Gummi Worm. Soft and smooth…

GSTs do not move very quickly. They often will eat then remain still for long periods of time. They don't seem to indulge in as many leaves as other butterfly larvae. They are considered a pest, however, particularly to citrus farmers. The nickname given to the larvae is 'Orange Dogs' by those who work in nurseries or citrus groves.

When it is time to pupate, the GST will make a silken harness and hang at a diagonal, right-side up (not hang upside-down in the ‘J’ position). The pupa is a light brown/tan colour and looks as if it has horns. I have always thought the pupa looks as if it has as a scowling face…

Side Note:

I have found that there are many people who work in nurseries who did not realize that the 'Orange Dog' was the larvae of the Giant Swallowtail butterfly! They just thought it was a terrible pest that must be eradicated. When I’d happily share my ‘find of a GST larva the workers often want to throw them in the trash!

Gender ID the Giant Swallowtail Pupae

It is easy to identify the gender of the pupa (chrysalis) of a Heraclides cresphontes IF you know what to look for. All you have to do is this: Check the end of the abdomen. That’s right! 

The picture shows what to look for. The female pupa has an obvious line whereas the male does not. Note that the abdomen is facing downward on a GST pupa and the picture on the right has both the female and male pupae turned sideways and the heads are on the right.

How long from egg to butterfly?

If you wondered how long it takes for a Giant Swallowtail butterfly then the answer is: who knows? Swallowtails, as a species, are unpredictable. Sometimes, you will have a butterfly eclose ‘on time.’ Other times, the butterflies will take their own sweet time and eclose, oh, when you least expect it, like…months later! The Giant Swallowtail overwinters as a pupa so if your butterfly hasn’t eclosed after the usual two weeks, then don’t worry. Chances are that it is in diapause and is just waiting for its perfect time. The BGEditor has had some in diapause for 8+ months.

The Birth of a Heraclides cresphontes

Nothing is more exciting than watching the birth of a baby. When that baby is a new butterfly, well, it is just spellbinding!

Watch the birth of a Giant Swallowtail, in pictures.

The caterpillar makes a little hole in the eggshell (chorion).

It’s little head is the first to come out of the hole. You can see little fuzzy ‘hairs’ on the outer portion of the caterpillar.

Almost completely out!

Here you can really see the head as it curls up around the outside of the eggshell.

Even at birth, the osmeterium is developed.

Ready for food! The first thing the little one will do is turn around to eat its eggshell. Then, it will go off to eat leaves.

Special Note regarding Rue (Ruta graveolens)

Rue (Ruta graveolens) is an herb in the Rutaceae family (Rutaceae family members include citrus plants like the orange, lemon, tangerine, kumquat,…). It is a fragrant, aromatic herb that has been used in some cultures for medicinal purposes as well as in cooking. As a bushy host plant for the Giant Swallowtail, it is a lovely plant to have in the garden that does well in part-sun/part-shade, requiring regular watering.

There is a dark side to this host plant that gardeners should be cautioned about. The plant contains oils that can cause severe gastric disturbances if ingested so if you have pets that may be apt to eat it, use care. If large quantities are consumed, it can cause death from liver/kidney failure.

The oils also contain chemicals that can cause either a dermatologic allergic reaction OR redness, blistering (like a burn), and hyper-pigmentation. The oils are found throughout the plant but especially in the leaves. Some people will simply get itchy when they come into contact with the leaves. Then, from the psoralens or furocoumarins, which are photo-active chemicals (have a chemical reaction when they are exposed to the sun), some people may find their skin reddening and then, several days later, forming blisters as though having been burned by a fire. Eventually, the skin darkens (hyper-pigmentation). This happened to me, as shown by the picture of the top of my hand.

I have had several people email me regarding this herb and what they’ve experienced. I recommend using gloves when handling it and immediately washing your hands with hot soap and water afterwards. Also, do NOT go out into the sun afterwards in case there are areas that the plant may have touched your skin that you are not award of. It is better to be safe than sorry later.

IF you do get ‘burned’ by Rue, the remedy is to apply a cortisone cream and keep the area out of the sunlight.


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DJInkers clip art is used with permission.