Cicadas are sometimes called locusts, but that term is more properly reserved for certain species of migrating grasshoppers. The two specimens in the display case are adults. (If you find any insect with functioning wings, it is an adult.)
top and bottom view of one of cicadas in Display Case
As you can see, adult cicadas are dark, chunky looking, moderately large, winged insects. As with all insects, they have 6 legs attached to the thorax (chest region) of the body. No legs are attached to the abdomen. The 2 pairs of clear wings are also attached to the thorax (some species do have some color in their wings). The front wings are larger than the hind wings.
In the picture of the underside of the insect, you can see that he is equipped with a needle-like beak. The beak can be inserted into a plant and used like a straw to draw up the plant's juices.
The species pictured is one that produces loud whines. As far as I could tell after watching one of these males, the triangular yellowish plates behind the last pair of legs can be involved in sound production. He seemed use these, along with his position on the branch (raising and lowering his body) to help control the quality of the sound. These plates also appear to provide some protection for the hearing and sound-generating organs.
Cicadas have a three stage life cycle - egg, juvenile or nymph, and adult.
The eggs are usually deposited in slits made in the twigs of trees and shrubs (some species use grasses). (It is not clear to me that the eggs are necessarily laid on the species of plant that the nymphs will eventually feed on). After hatching each nymph falls to the ground, and spends the rest of its life, up to 17 years for some species, underground among the roots of the host plant sucking up plant juices. When the time is right, the nymph works its way to the surface, locks its body onto some suitable support, and molts (sheds its skin) for the last time (all juvenile insects molt a number of times as they grow), emerging as a relatively short-lived adult.
pictures of cicada exuviae (molted skins)
It is the adults that we are most familiar with. Their sole purpose is to find a mate so they can reproduce, and this process is completed in about a month. Of course, during that time period many become food for various birds, reptiles and other insects. (The Cicada Killer wasp uses paralyzed cicadas as food for its young.) The adult males advertise for receptive females with their loud sounds. Because of the large number of males calling in an area at one time, the sound can be quite loud. As their numbers start to decline, the trails become much quieter.
At least two species were involved, but it is possible that there were more.
Look for the empty, cast off skins. These can remain on the molting support for a long period of time, depending on the weather. The support can be just about anything that is strong enough, but many insects prefer bark or branches. If you find one empty skin, there is a good chance that more will be present nearby, since host plants often support many nymphs developing from eggs laid at the same time. Check the area on successive days - not everyone will emerge on the same night but mass emergences do occur. You may find a new, fragile, pale-looking adult close by. It takes time, sometimes several hours, for the new wings and body to expand and harden sufficiently for the rigors of flight. During this period, the insect is extremely susceptible to weather damage and predation because it must sit and wait.
Listen for the calls. Use both ears and turn your head back and forth to isolate the tree or shrub that the loudest sound appears to be coming from. It might help to cup your ears with your hands. Calling cicadas are often not right out in the open, but instead are hidden inside the plant, pressed up against a branch. Look for a lump that seems out of place. It's fun, but it can be very frustrating. Try the Texas Madrone and Grey Oaks along the boardwalk to the Visitor Center - a number of calling males seem to like them.
Watch for flying cicadas. As they zoom around between the bushes, their bulky size reminds me of a large, dark carpenter bees. (One species found in the more open areas here shows a lot of white when it flies.) If you can pinpoint which tree or shrub an insect lands on, then you can look for it. Chasing flying cicadas is not advised, since it is difficult to watch your footing and the insect at the same time. (In the park of course, there are numerous other hazards like cacti and snakes you also need to watch for.) In addition, cicadas can fly long distances and are extremely fast.
Look for the periodical cicada web site. This site deals with the 17 and 13 year cycles of the various broods of cicadas familiar to many people living in the eastern states.
Note: This is a personal web site and is not affiliated with the National Park Service or Guadalupe Mountains National Park. Contact information for the author, Ron Lyons, is accessible through the Index Page referenced below. Thank you.