Eggs in the Yard

Notice the small things. The rewards are inversely proportional.

~Liz Vassey

While sitting out in the yard last week, we noticed a butterfly flitting around a few plants at the edge of the woods, a flight pattern that usually indicates it is a female looking for a place to lay an egg. The butterfly was an Eastern tiger swallowtail, so we knew she was looking for either a tulip poplar or a wild cherry, the two common host plants in these woods. She finally landed on a tulip poplar leaf, paused for a couple of seconds, and flew off. Melissa ran over to look, and after searching for a minute, found an egg.

Eastern tiger swallowatil egg with finger for scale

Eastern tiger swallowtail egg (click photos to enlarge)

Finding butterfly eggs can be relatively easy if you find a female butterfly hovering near her host plants. They usually flit around, twisting and turning, as if searching for something (which they are). They may land on a leaf for a second, “tasting” the leaf with chemoreceptors in their “feet”, to see if this plant is the right one. If not, they move on. If it is, then she may curl her abdomen and linger for a second, attaching an egg in the process. The female secretes an adhesive substance to secure the egg to the leaf.

tiger swallowtail egg

Eastern tiger swallowtail egg on a tulip poplar leaf

Eastern tiger swallowtails lay a greenish egg that blends very well with the leaf surface, making it tough to spot. The past few days I searched a few more tulip poplar saplings at the edge of the yard and came up with a couple of more eggs.

Tulip poplar leaf with egg wide view

Can you see the swallowtail egg on this leaf?

 Hint…click on the image to enlarge…it is on the right side of the leaf.
Tiger swallowtail egg close up

Close up of Eastern tiger swallowtail egg

Swallowtail eggs are somewhat spherical, although the base is a bit flattened where it attaches to the leaf surface. Unlike many other butterfly eggs I have seen, swallowtail eggs lack ridges, spikes, or other sculptural elements that can give insect eggs such exquisite shapes. But, in their simplicity, they are both gorgeous and elegant.

tigr swallowtail first instar 1

First instar larva of Eastern tiger swallowtail (very recently hatched)

Large numbers of tiger swallowtails are flying this spring, so I would have expected to find even more eggs and larvae than we have. But, this forest is dominated by huge tulip poplars, so I imagine most of the egg-laying occurs high up in the canopy, far beyond the peering eyes of a couple of egg hunters. Over the past couple of days we did find a couple of recently hatched larvae down low, so I grabbed a few photos of these bird poop mimics.

Tiger swallowtail early instar 2

Early instar, “bird poop mimic”, of Eastern tiger swallowtail

bird poop

Real bird poop on a poplar leaf (probably don’t want to click on this photo)

I even found a couple of leaves with real bird poop, and I couldn’t resist sharing the similarity to our little caterpillars.

Tiger swallowtail early instar 1

Curled caterpillar looking like some bird poop. Note the silk pad the larva has created on the leaf for attachment.

The combination of a dark background color with a white patch on these larvae does make for a distasteful-looking  mimic.
tiger swallowtail third instar

Later instar (third?) of Eastern tiger swallowtail

Yesterday evening, we found where one of the dark bird poop mimics had already molted into a green version, suspended above the leaf surface on their characteristic silk pad. The larval stage of this species lasts about two weeks and they molt five times as they progress from newly hatched caterpillar to chrysalis.

zebra swallowtail egg

Zebra swallowtail egg on underside of pawpaw leaf

The yard has a variety of host plants for different species of butterflies and moths, so I decided to check for eggs of a couple of other swallowtail species. The small stand of pawpaw is usually good for a couple of larvae of the beautiful zebra swallowtail butterflies. This species lays its eggs on the underside of the leaves, so I started searching and eventually found a few eggs. They are white to cream-colored, and usually placed near the edge of the leaf, which makes sense, since the female lands on top of the leaf and then curls her abdomen underneath to lay the egg

zebra swallowtil first instar wide view

Freshly hatched larva of zebra swallowtail (which dark spot is the caterpillar?)

Yesterday, I again looked for the eggs and found freshly hatched larvae, the smallest ones I have ever seen. Zebra swallowtail larvae are black in the first couple of instars.

Zebra swallowtil first instar

First instar (recent hatch) of zebra swallowtail

A closer view shows they lack a large white patch so common in the other larvae that mimic bird droppings.

Spicebush swalloewtail egg laid same day

Spicebush swallowtail egg on the underside of a spicebush leaf

As luck would have it, while eating lunch yesterday, I saw a dark swallowtail hovering around plants, obviously looking for that special place to deposit an egg. She eventually made her way to an isolated spicebush shrub, and began laying. She flitted from one leaf to another, eventually laying three eggs on that shrub, one each on the underside of three different leaves. These eggs look similar to those of the zebra swallowtail, although perhaps a tiny bit larger.

I checked my parsley and fennel leaves in the garden, but no signs yet of black swallowtail eggs, so I will have to be content with three species of swallowtails for the time being. Still, this is a great start to my favorite time of the year – caterpillar season. It reminded me of a post I did last summer after finding three species of swallowtail caterpillars in one day. But I’ll keep looking at the parsley and the pipevine to see if I can break that record and maybe get to a five cat day this year.





Beauty in Miniature

Find beauty in the small things…

~author unknown

It is the time of year when I turn my attention to caterpillars (BugFest is approaching). So, I am always glancing at shrubs and trees that I know are host plants to see what might be happening. There is a small Black Cherry tree out back and it has been a hot spot for various critters this summer. This morning I saw several leaves that looked like this…

Red-spotted Purple egg on cherry leaf

Red-spotted Purple egg on Black Cherry leaf (click photos to enlarge)

A tiny white blob on the tip of several leaves. This is a sure sign of activity by a female Red-spotted Purple Butterfly (Limenitis arthemis astyanax). Why they lay on the leaf tip is unknown to me, but it sure makes them easier to find than the eggs of many other species.

Red-spotted Purple egg up close

Red-spotted Purple egg up close (a strand of spider silk has caught on the egg as well)

I took a few images with my super macro lens (Canon MP-E 65mm) and you can see the delicate patterning on the egg surface (too bad it is such a shallow depth of field). It is sculptured with small hexagons with spikes arising from the corners. The purpose of this sculpturing may be to increase the surface area of the egg to facilitate the exchange of gases for the developing embryo. Or it may be to make people like me happy when we bother to look closely.

rsp egg up close

Even closer

An even closer look shows some additional structure in one of the hexagons that probably corresponds to the top of the egg. Look just above and to the right where the spider silk is attached and you may see one hexagon that has a small series of bumps in it. This may be the perforations known as micropyles, where sperm enters the egg. These serve as gas exchange areas as well. As quoted in a great natural history book entitled, Butterflies and Day-flying Moths of Great Britain and Europe

The cut-glass delicacy of these eggs, described by Edwin Newman more than a century ago as “a thousand times more delicate and fine than any human hand could execute”, is truly one of nature’s marvels.

Is This a ? Egg?

Butterfly in egg-laying behavior

Butterfly that was laying eggs in a patch of False Nettle (click photos to enlarge)

I glanced out the back of the screen porch the other day and saw a butterfly behaving as if it were going to lay eggs – that typical fluttery flight around a plant that indicates she is searching for just the right spot to lay an egg.

False Nettle

False Nettle, Boehmeria cylindrica

The butterfly was one of the anglewings – either a Question Mark or an Eastern Comma, and the plants were some False Nettles (one of the anglewings’ host plants) mixed in with some ferns and other moisture-loving plants in a shady, wet drainage area out back. I have been seeing Eastern Commas feeding on the figs in the garden but this one would not slow down long enough for me to see any details on the wings to make a clear identification. I went inside and grabbed the camera with the 300mm and an extension tube and fired off several shots as the butterfly flitted about quickly laying an egg here and there on the undersides of leaves.

Question Mark confirmed

Question Mark confirmed

I often use the camera to help me identify species that are moving too quickly for a good view. Once you look at images on the computer, you can often see identifying characteristics more clearly. Such was the case in one photo this time – I could just make out the distinct marking on the underside of the wing that identified the egg-layer as a Question Mark, Polygonia interrogationis.

Question Mark egg 2

Freshly laid Question Mark egg on underside of False Nettle leaf

I went back outside and started turning over leaves looking for eggs and finally found one  – a very small greenish egg sculpted with vertical ridges. The eggs of Question Marks and Eastern Commas are identical so seeing the egg-layer is important for identification. In reading about these two closely related species, I found an interesting note about their eggs – females often lay eggs in short stacks, one egg on top of the other, in stacks of a few up to 8 or 9 eggs. Naturally, I went back out to see if I could find any.

Question Mark egg 5

Dark egg of an anglewing

My first find was a single darker-colored egg on the same plant. I assume it is an egg that was laid earlier and may be getting ready to hatch as I have seen other species’ eggs darken prior to hatching. I suppose the other possibility is that the egg has been parastized by something. I’ll have to wait and see.

Question Mark egg stack of 2

Egg stack

After searching the False Nettles for eggs and only finding singles, I went up to the garden to check another host plant that I know is growing up there – a Winged Elm sapling. Question Marks and Commas have three common host plants in our area – False Nettle, Stinging Nettle, and elms. The first leaf I looked under had a short stack of two dark eggs. There were lots of eggs on this tiny sapling, perhaps due to the abundance of decaying figs in the adjacent trees that attracted the butterflies to the area.

Question Mark egg stack of 3 b

Egg stack on underside of elm leaf

It wasn’t until I had set up to photograph the stack of two eggs that I noticed a cluster of eggs on a curled leaf at the tip of the branch, including a stack of three eggs. It looks so strange and even though I searched the internet  and all of my reference books, I came up with no clear explanation as to why these species stack their eggs. Some butterflies, such as the Pipevine Swallowtail, have larvae that contain toxins and lay their brightly-colored (warning colors like orange or red) eggs in clusters. Their distasteful caterpillars usually feed in groups which may afford them more protection from predators. I also found a  reference to a species in England whose stacks of eggs are said to resemble the flower parts of the host pant, thus camouflaging the eggs to a certain degree. None of these explanations seems to quite fit in this case, so the reason for egg stacking remains a mystery to me.

Black Swallowtail eggs

Black Swallowtail egg on fennel

Black Swallowtail egg on Bronze Fennel (click to enlarge)

As I was planting some veggies yesterday, I saw a female Black Swallowtail butterfly in her characteristic search and hover mode as she investigated various plants in the garden. I knew from this fluttery flight behavior that she was searching for the right type of plant on which to lay an egg (aka host plant). As with many species of butterflies and moths, Black Swallowtail females tend to be discerning when it comes to which plants they choose for their eggs. Host plants of the caterpillar include members of the parsley family (Apiaceae) including Carrot, Parsley, Dill, Fennel and Queen Anne’s lace and some members of the Rutaceae such as common garden Rue (Ruta graveolens).

I have four of these in the garden right now: Parsley, Bronze Fennel, Sweet Fennel, and Rue. From my experience, the Bronze Fennel seems to be the preferred host, especially early in the season. The tops of the Carrots I grew last year were also very popular with the caterpillars. As any herb gardener knows all too well, Parsley is also immensely popular as a host plant, with the larvae often totally denuding your herb supply if you only have a few plants. That is one reason I plant the fennels as they tend to get tall (3 or 4 feet) which is usually enough to provide an adequate food supply. Rue becomes especially important as a host plant in my garden in the late summer and early fall as Black Swallowtails complete their final generation before winter. Last year I had one large rue plant with over 20 caterpillars on it and rue tends to be less completely devoured compared to some of the other hosts. Rue stems also tend to sprout quickly after being eaten. But I have also read that Rue can cause skin irritation in sensitive people, so be cautious if you plant it.

Bronze Fennel

Bronze Fennel (click to enlarge)

Sweet Fennel

Sweet Fennel (click to enlarge)


Parsley (click to enlarge)


Rue (click to enlarge)


Close-up of Rue foliage (click to enlarge)

Naturally, I was excited to see what I thought were the first butterfly eggs of the season in the garden. I grabbed my camera and took a few shots after finding eggs on several fennel and parsley plants. The eggs are spherical and cream-colored (or slightly yellowish). The other swallowtail species eggs I have seen are also spherical although different species tend to have different colors. The eggs of other butterfly and moth groups can be quite ornate with many shapes, colors, and ornamentations (perhaps a blog topic later this season). Each butterfly egg is surrounded by a hard outer shell, called the chorion, to protect the developing larva. The shell is lined with a layer of wax, which helps keep the egg from drying out. There is a small opening near one end called a micropyle, which allows sperm to enter the egg for fertilization. The egg shell also is dotted with microscopic pores called aeropyles which allow gas exchange. The butterfly glues the egg to the plant leaf using an adhesive-like substance produced in the colleterial glands. Black Swallowtails lay the eggs singly (generally on the top of leaves) although she may lay several eggs on the same plant.

Black Swallowtail egg on parsley

Black Swallowtail egg on parsley (click to enlarge)

As I wandered the garden looking for more eggs, I realized the one I photographed is not the first of the season…I found a tiny caterpillar on one of the Rue plants. Since it takes 3-5 days for these eggs to hatch, I had apparently missed a few from the past weekend.

First instar Black Swallowtail larva

First instar Black Swallowtail larva (click to enlarge)

This is what is known as the first instar larva, the stage after emergence from the egg. It looks quite different from how this species is pictured in most caterpillar field guides. As is common with many species, Black Swallowtail caterpillars undergo a noticeable change in appearance as they molt five times on their way to becoming a chrysalis. This early stage is considered a bird poop mimic, with a dark background color containing a whitish splotch, just like a bird dropping. Many other species have this basic color scheme, especially as early stage larvae.

Black Swallowtail caterpillar next to pencil point

Black Swallowtail caterpillar next to pencil point (click to enlarge)

I’ll hang onto this little guy and try to photograph it as it develops over the next couple of weeks. I think I’ll have plenty of opportunity to get the various life stages as I found 11 eggs (and two more first instar larvae) on one Bronze Fennel plant this morning.  While searching the Internet for a few details on these eggs, I found what could be my moneymaker in retirement – seem like a few companies sell butterfly eggs for people to raise and I saw one site that had Black Swallowtail eggs for $2 each! If I had the time and inclination, it could be a busy (and profitable) summer.