Kids blow bubbles for fun — spittlebugs because they must


One of my favorite outdoor activities with small children is blowing bubbles. Yes, you can buy the solution — nothing more than water and dishwashing soap — in small containers that contain the little wands.

The bubble of air is enclosed by a three-layer soap film. There is a layer of soap on both the outside and the inside, with a layer of water sandwiched in between. The bubble pops when the water layer evaporates.

To make a stronger and higher-flying bubble, you need to add corn syrup or glycerin. These two ingredients make the soap layers stronger and thicker and reduce the evaporation rate, allowing larger bubbles to  form. Unfortunately, the addition of glycerin and corn syrup reduces the amount of reflective colors.

There is even one recipe that deletes the corn syrup but adds dry gelatin into the solution, creating a very strong, long-lasting bubble. However, it is heavier than the other types, and so it will not fly away over the treetops.

Foams, including soap bubbles, are structures where gas is trapped inside a liquid or solid. Generally, foam is classified into two types — open or closed cell. Closed cell foams form separate air pockets surrounded by a more solid material, while in open cell foams, the pockets interconnect.

An unexpected example of a common foam is bread. For the bread bakers among you, you already know that yeast creates discrete air pockets within the bread dough as the dough rises. This is a closed cell situation as demonstrated by the fact that cutting through the dough releases a limited amount of gas.

However, if the dough over-rises, it becomes transformed into an open cell structure, which is why if the dough is cut, the entire mass collapses. When the properly risen dough is baked, it transforms from a closed cell to an open cell structure.

With that lengthy introduction, we are finally able to return to a white foam I found while prospecting for Alliaria petiolata plants in Riverdale. Turning to two of my gurus, they corroborated each other and said it was clearly caused by spittlebugs (froghoppers), originally classified as a sub-order of Hemiptera and named homoptera. Meanwhile, based on molecular studies, the former homoptera have been split into three sub-orders of Hemiptera, while the term homoptera is now only used as a popular term to describe plant-feeding Hemiptera such as aphids.

Meanwhile, our spittlebugs have been placed in sub-order auchenorrhyncha, family Cercopidae.

The popular term “froghopper” comes from the ability of adults to jump to a height of up to 115 times their body length. The etymology of auchenorrhyncha is thought to come from the ancient Greek where aukhen is the throat or neck, and rhynchos is a snout or beak.

It is not clear how the term came into use since the usual insect body divisions of head, thorax and abdomen are not clearly obvious in describing these insects. However, Philip Matthews — who has done research on the spittlebug Philaenus spumarius — claims they “have big bulbous noses.”

At least one type of Hemipteran fossil has been found in Colorado from the Oligocene (from between 23 and 33.9 million years ago).

Spittle, frequently shortened to “spit,” is another word for “saliva.” This foam is sometimes referred to, also, as “cuckoo spit.” Overwintering eggs, which are deposited in the late summer on stems near the soil surface, hatch in early to mid-spring, and the nymphs (juvenile form) produce the foam, which is derived from a “mixture of a fluid voided through the anus plus a mucilaginous substance produced by epidermal glands,” which stabilizes the foam.

Some species can produce 80 bubbles per minute.

Although the bubbles are filled with air, the insect actually is breathing by sticking its abdomen through the foam to the outside. The insect can make use of the internal air supply if the foam should be submerged.

The purpose of the foam, however, is protective. It insulates the insect from temperature extremes and prevents desiccation when the humidity is low. It also protects against predators.

The nymphs molt two to four times before becoming an adult. The juveniles as well as the adults feed on plant fluids, but unlike most plant-suckers, they concentrate on fluid from the xylem (which carries water and nutrients from the soil throughout the plant) instead of the phloem (which carries photosynthetic products down from the leaves).

The insects are seen on a wide variety of other plants, including roses, goldenrod, pines, spruce and fir trees.

It will probably not come as a surprise that other animals use foam creatively. The arboreal (tree-living) gray foam-nest tree frog uses foam to protect its eggs during development. Many fish create what are known as bubble nests as places where eggs can be deposited, properly aerated and guarded until hatching.


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