The art of spitting...

The other afternoon while walking along the Little Miami River, I saw plant after plant covered in frothy bubbles of spit. From a distance, the globs looked pretty gross, but up close, they just looked pretty...

Bubble art is created by a tiny nymph called a spittlebug. The glob of soapy froth functions as the nymph's home while it matures. The froth keeps it hidden from predators and prevents it from drying out in the sun as the nymph feeds on the plant.

A spittlebug is the nymph stage of a tiny insect called a froghopper. Female froghoppers lay eggs in late summer on plants. The eggs are impervious to cold and frost, so they last through the winter. In the Spring, the eggs hatch out, and the nymphs attach themselves and start eating and creating bubbles from the plant's sap. These bubbles provide protection and moisture, and the nymph will hide and live in the glob until it's an adult. Predators can't see the nymph in the foam, and because it has a bad taste, predators tend to leave it alone. The foam also insulates the nymphs from the drastic temperature changes associated with spring, and the moisture keeps them from drying out in the hot sun as summer comes along.

"Welcome to my foam home," said the spittlebug. Common names for the frothy, spit-like mass are frog spit, snake spit, and cuckoo spit. The foamy bubbles are a little sticky and don't break up easily. They are not like "real" spit.

For a more detailed account of spittlebugs, click here for an article written by Roy Lukes titled "The Insect Whose Babies Live in a Bubble."

What is a nymph?
A nymph is the juvenile stage of an insect that undergoes simple metamorphosis. Eggs hatch into nymphs, which resemble adults but have no wings.

Differences between complete and simple metamorphosis...
Butterflies undergo complete metamorphosis. We are all familiar with the lifecycle of a butterfly, which goes from an egg, to a caterpillar (larva), which spins a cocoon (pupa), to an adult butterfly. In complete metamorphosis, the adult looks completely different from the larva.

Spittlebugs undergo simple metamorphosis. Their lifecycle goes from an egg to a nymph, to an adult. In simple metamorphosis, the adult looks similar to the nymph.

What is an instar?
Both nymphs and larvae go through instars. Nymphs and larvae eat and eat until they burst out of their exoskeletons and molt into slightly larger versions of themselves. The stages between molts are called instars. Nymphs (simple metamorphosis) molt into adults from their last instar, but larvae (complete metamorphosis) pupate in a cocoon after their last instar before emerging as completely different adults. Spittlebugs usually go through about five instars before becoming adults (can vary with species)

For an illustration that shows examples of instars in complete and simple metamorphosis, click here.
For an earlier post I did that shows several instars of Large Milkweed Bugs, click here.

How does the nymph manufacture the bubbles?
I didn't know how the nymph created the spit, but a quick look in my Kaufman Field Guide to Insects of North America, pg 94 (by Kenn Kaufman and Eric Eaton) clued me in. The nymphs use liquid waste products from the sap they have been feeding on mixed with mucous they secrete. They have tiny fingerlike projections near their hind end at the tip of their abdomen that they use to pull in air that mixes with the liquid to create the bubbles.

For a cool video of nymphs walking in and out of the foam, click here.
For a video of a nymph creating bubbles, click here.

Large Milkweed Bugs (Oncopeltus fasciatus) at Fort Ancient

A few weeks ago I spent a little time hiking through the meadow by the Mound Trail at Fort Ancient. The grasses were brown and dry, and what was left of summer's bounty crackled and rattled with each breeze that worked itself through the tumble of spent flower heads and stalks. Autumn had drained the green from the landscape, and even the yellows had faded from the fields, but oranges and reds were still around to be found on the dry and cracked Common Milkweed plants...

An adult Large Milkweed Bug (Oncopeltus fasciatus) is surrounded by all five of its instars. The adult is at the top. It is the largest and has usable wings. Instars are nymphs, or immature versions of the bug. Instars differ in size, color and pattern. They also lack usable wings.

Large Milkweed bugs molt five times (nymphal instars) before they become adults. During these stages the nymphs look similar to the adults; however, if you look closely you can see each instar has its own color (from deep red to orange) and pattern. During the middle instars black wing pads start to form, but the wings are not usable until the fifth instar molts into an adult.

...also unique to the adult is the flame-red pattern on its face between its eyes...

...the adult Large Milkweed bug has a striking pattern of orange and black on its wings. Here you can see the veins that carry the hemolymph through the wings. On the final molt, the adult Milkweed bug pumps hemolymph through these veins to unfurl the wings. To see an adult who failed to open his wings, click here.

...a fifth instar almost looks like an adult, but lacks the defined face pattern, usable wings, and the eyes are much less "buggy!" Look to the right for a glimpse at an adult's eye.

One adult and several fifth instars mass together to form a color warning on an old Common Milkweed pod.

Since Large Milkweed bugs eat Common Milkweed sap, which contains toxic alkaloids, they do not taste good. A young bird only has to taste this bug once or twice to learn to avoid orange and black bugs! Large groupings of this color combination warn birds away. You may already know of another orange and black insect that has the same type of protection--the Monarch butterfly. Just like the Large Milkweed bug, Monarch butterfly caterpillars feed on Common Milkweed plants and concentrate the alkaloids in their tissue. When the caterpillars metamorphose into Monarch butterflies, they are toxic and also taste bad.

Another tidbit...I read on this site (click here) of an easy way to distinguish between a male and female milkweed bug--the female Milkweed bug has one black strip and two back dots on her abdomen, while a male has two thick black strips. I didn't know that before and never flipped one over to look. Next time I see one I'll take a peak.

...close-up of two later instars.

...close-up of an adult Milkweed bug--love the face tattoo.

This guy is not going to be hanging around much longer. These bugs migrate! Just like the Monarchs, they head south for the winter. Shorter days in autumn trigger diapause in the adults, which shuts down the reproductive system (source: "Migration: the biology of life on the move," by Hugh Dingle, page 139, click here to read more.). Shutting down the reproductive system saves energy and allows the Large Milkweed bugs and Monarch butterflies to migrate south for the winter. The same adult Milkweed bugs that overwintered in the south then migrate back north in the spring to lay the eggs of the next generation.

If you want to learn more about the Common Milkweed plant and all the insects that feed on it, check out this post by Marcia Bonta. I stumbled across it a few weeks ago and thought it would fit in here. For more photos of Large Milkweed Bugs, click here for an earlier post.