Cicada Cycles

A Cactus Dodger cicada found in Big Bend National Park, TX

A sure sign that we are in the midst of a hot summer is the sound of cicadas buzzing in the air.  For their size, cicadas make as much noise as a large animal, and can be heard up to a quarter of a mile away.  In fact, the word ‘cicada’ is a direct derivation from the Latin meaning ‘buzzer.’ 

Most species of cicadas in North America are in the genus Tibicen, and are generally called the annual or ‘dog-day’ cicadas because they emerge every year in July and August, the dog days of summer.  More widely known are the periodical cicadas from the genus Magicicada, who have a very long lifecycle of 13 to 17 years, and when they emerge, do so in great numbers.     

Tibicen resh, cicada found in Austin, TX

Male cicadas have structures called ‘timbals’ on the sides of their abdomens, and it is with these structures that they create their buzzy songs.  Unlike grasshoppers or crickets that rub their wings or legs together to produce sound, cicadas vibrate these timbals against their hollow abdomens which amplifies the resonance of the sounds.  They can even modulate the sounds by wiggling their abdomens toward or away from the tree trunk on which they are perched.  Each species has its own distinctive sound, and they use different mating songs to attract the appropriate mate.

The lifecycle of a cicada is quite fascinating.  After mating, females deposit hundreds of eggs in a slit made in the bark of a twig, normally on an oak tree.  When the eggs hatch, the nymphs drop to the ground and burrow from 1 to 8 feet, feeding on the juices of the tree roots.  These nymphs spend most of their lives underground, from 2 up to 17 years, depending on the species.  The nymphs then construct an exit tunnel to return to the surface in mid-summer, molt or shed their skin on the bark of the tree, and emerge as adults.  These adult insects are usually 1-2 inches long, have prominent, wide-set eyes, short antennae, and transparent, membranous front wings.   

Empty shell of newly emerged Tibicen resh cicada

While there are over 40 species of cicadas in Texas, the late summer afternoon air in Austin vibrates with the sounds of several annual cicada species such as Tibicen resh (which has no common name) and the Superb Green Cicada (Tibicen superba).  Once every 13 years, the periodical cicadas Magicicada septendecula (which also have no common name) emerges but they are becoming increasingly scarce.  

Cicadas go by a number of common names: locusts (which is technically not correct as cicadas are unrelated to true locusts which are part of the grasshopper family), jar flies (for the way they vibrate or ‘jar’ when held in the hand), June bugs or July flies (in the southeastern US), heat bugs (in Canada and the mid-West), and dry flies (in parts of the southern Appalachian mountains for the shell they leave behind).  Whatever you call them, you’ll be sure to hear and see them in the heat of a Central Texas summer! 

Turtle Teachings

Texas Cooter, Pseudemys texana

Hardly a day goes by in the summer months when you can't find a turtle basking in the sun.  Like other reptiles, turtles are cold-blooded or ectotherms, who vary their internal temperature according to the ambient environment.  Turtles have been around for over 250 million years, even longer than their snake and lizard relatives.  We tend to use the word turtle for all freshwater and some land-dwelling species, while tortoise is used only to describe members of the true tortoise family.

Red-eared Slider, Trachemys scripta elegans

The shell of a turtle has two parts:  the upper is called the carapace, while the lower is called the plastron.  Many turtles have a bony bridge that connects the top and bottom and lends strength and rigidity to the structure.  Carapaces of turtles vary widely, and shape, colors, and patterns are among the field marks that often distinguish one species from another.  Scutes, from the Latin scutum or shield, are the plates which cloak the outside of the turtle's shell.  Most turtles have 54 scutes, with 38 covering the carapace, and 16 covering the plastron.  Made from the protein keratin, scutes can be thought of as the epidermis that covers the bony shell.  It is even possible, by counting the stack of smaller, older scutes on top of the larger, newer ones, to estimate the age of a turtle.  The accuracy of this method, however, is somewhat muddled by the variable growth rate of the scutes and the fact that, like fingernails or horns, they eventually fall away from the shell.  

Texas Cooter, Pseudemys texana

Regardless of the length of a turtle’s neck, they all have 8 vertebrae.  In spite of their highly muscular necks, turtles are often called ‘hidden-necks’, for their ability to retract their head and neck into the shell by bending it into a vertical S-curve and withdrawing from sight.  Some species like box turtles go even further, and gain an added degree of protection from predators by having a hinge in their plastron, dividing it into two lobes, and giving them the ability to draw up those lobes and completely seal the turtle inside.

Eastern Box Turtle, Terrapene carolina

Turtles may spend most of their life in or around water, but they breathe air and often range widely when searching for a mate in the warmer months.  With smell being the keenest sense possessed by a turtle, the males will chase any object of approximately the correct size, and once close, will use smell to determine if the object is a female of the same species.  Pregnant females will dig a hole, often called a body pit, and deposit eggs in the hole, covering them with dirt.  In some species of turtles, temperature determines whether an egg develops into a male or a female, with a higher temperature producing a female and a lower temperature producing a male.  Hatchlings squirm their way to the surface and head toward water alone, as there is no known turtle species where the female cares for the young. 

Spiny Softshell Turtle, Apalone spinifera

The more common turtles you will see in central Texas include the Common snapping turtle (Chelydra serpetina), Eastern box turtle (Terrapene carolina), Red-eared slider (Trachemys scripta elegans), Texas map turtle (Graptemys versa), and the Spiny softshell (Apalone spinifera).  All but the box turtle are generally found in wetlands, ponds, streams, and lakes where heavy vegetation is present, although box turtles are activated by rain events. 

Symbolically, the turtle has represented patience, strength, endurance, stability, and protection to many native peoples, who have observed the often slow but deliberate life of the turtle.  This is a fascinating fact, since researchers have recently discovered that turtles’ major organs, such as the liver, lungs, and kidneys, do not gradually break down or become less efficient over time.  Understandably, this has inspired geneticists to begin a detailed study of the turtle genome, hoping it can unlock the secrets of longevity!   

Spiders on the Prowl

Green Lynx Spider, Peucetia viridans 

An often seen spider in our suburban yards and gardens is the black and yellow garden spider (Argiope aurantia).   True to its common name, this spider has distinctive black and yellow (and sometimes orange) markings on its abdomen and a mostly white area behind its head.  With a fairly rotund body of 1 ½ inches in length, the females of this species are twice as large as the males (common for most spiders), and can have colorful banding on the legs.  These spiders are active during the summer months, and tend to be somewhat local, staying in one place throughout much of their lifetime.  Like other members of the Argiope family, they are considered harmless to humans.  

Black and Yellow Garden Spider, Argiope aurantia

These garden spiders have three claws on each foot, unlike most spiders that have only two claws, and the extra claw helps them to spin complicated webs.  Many times these webs are built in areas adjacent to open sunny areas, often two to eight feet off the ground.  Most distinctively, the circular part of their webs are up to two feet in diameter, with a dense zigzag of silk, known as a stabilimentum, in the center.  While the purpose of this structure is disputed, it helps this spider earn its other common name, the writing spider.  It is most often thought that the stabilimentum might warn birds of the presence of the web, and only those spiders that are active during the day construct these types of patterns in their webs. 

Black and yellow garden spiders breed once a year. The males roam in search of a female, building a small web near or actually in the female's web, then court the females by plucking strands on her web.  When the male approaches the female, he often has a safety drop line ready, in case she attacks him. After mating, the male dies, and is sometimes then eaten by the female.  The female will then lay her eggs, cover them with a sheet of silk, roll them into a sac, and hang them from the center of her web, where she spends most of her time. She guards the eggs against predation as long as she is able, but as the weather cools, she becomes more frail, and dies around the time of the first hard frost.  Come spring, the tiny young spiders exit the sac and disperse, often on a strand of silk carried by the wind.

Another common but startling-looking spider is the spiny-backed orbweaver, or spiny orb-weaver (Gasteracantha cancriformis).  Its shell is shaped like a crab shell, wide, flat and variably red, white, orange, or yellow with dark oval spots, rimmed by six red or orange spines.  The males lack these distinctive spines, having only four or five stubby dark projections, and are two-thirds smaller than the females.  Their Latin name comes from ‘cancer’ meaning ‘crab’ and ‘forma’ meaning ‘shape, form, or appearance.’

Spiny Orb-Weaver, Gasteracantha cancriformis

Also called a jewel or jewel box spider, this spider ranges across the southern half of the United States and is found year-round in woodland edges and shrubby areas of Texas.  It usually adds decorations or little tufts of silk to its web, possibly to warn birds and other animals of the web’s location.  A short-lived spider, its lifespan lasts until reproduction in the spring following their birth.  In fact, the males die only six days after mating with a female.

Often found feeding on flowers, the Green Lynx Spider (Peucetia viridans) is a bright green spider and the largest lynx spider in North America. The species name is derived from the Latin viridis, meaning ‘green’, and is its signature characteristic.  Its abdomen has a series of cream-colored chevrons along its length, with white stripes accented by russet margins.  Long, thin legs are pale green to yellow, and are covered with long black spines and spots.  Gravid females are able to change color to fit their background, and depend on this ability in September and October, to help them defend their egg sac filled with bright orange eggs, from predation.  

Green Lynx Spider, Peucetia viridans 

Active during late spring and summer in a wide variety of habitats, the Green Lynx spider does not spin a web, but hunts for moths and other small insects among low shrubs and plants.  As such, this spider is of great interest for its use in agricultural pest management, but unfortunately also preys on beneficial insects such as honey bees.  Very seldom does this spider bite humans, and its bite is harmless. 

Relatively common throughout Texas, tarantulas are our heaviest and largest spiders.  Typically, the head and legs are dark brown, and the abdomen is brownish-black.  Coloration varies between individuals as well as between the 14 different species found in our state.  Identification of species is difficult, however, and is often performed only on mature males under a microscope.

Tarantula crossing the road

Tarantulas are typically found in grasslands and semi-open areas, and use burrows, natural cavities under stones or fallen logs, spaces under loose tree bark, and even old rodent holes as shelters.  They are also capable of digging their own burrows, and often line them with webbing, placing a few strands across the front to help detect passing prey.  Laying several hundred eggs in a hammock-like web constructed inside the burrow, females will guard them until they hatch.  Females have lived in captivity for over 25 years, while males rarely live over two or three months after reaching maturity. 

Tarantula visiting our back porch

Other insects such as crickets, beetles, grasshoppers, cicadas, and caterpillars form the basic diet of the tarantula.  They inject their prey with a poison when they bite, which liquefies the prey’s insides, making it easier to ingest.  While they can climb, they are usually restricted to the ground, with the males actively wandering in large numbers in late summer, apparently seeking out females.  The hairiness and large size of tarantulas often evokes concern, but the bites of Texas species are not serious to humans.  Tarantulas maneuver quickly to face whatever disturbs them, often raising up on their hind legs and stretching out their front legs in a threatening posture.  They have also been observed rapidly brushing the top of their abdomen with their hind legs to dislodge hairs that can be used to irritate the attacker’s eyes or skin.

Tails of Summer

Giant Swallowtail, Papilio cresphontes

Flower blooms in summer are often visited by large, colorful butterflies in the swallowtail family. These insects are so named because of the tails on their hindwings that resemble the forked tails often found on birds in the swallow family.  They are even more unique when in the caterpillar stage, because they possess a hidden structure behind their heads called an ‘osmeterium’, a fork-shaped organ that is exposed when under threat (or forced out with a gentle squeeze) and can emit a smelly and bad-tasting secretion.  As such, swallowtails are distasteful to many predators in both the caterpillar and adult butterfly forms.

The smallest and darkest swallowtail you will see this time of year is the Pipevine Swallowtail (Battus philenor).  Its upperside has blackish-brown forewings and hindwings that have an iridescent metallic blue sheen.  The undersides of their hindwings have bright orange dots surrounded by black and blue, with subtle white markings.  The Pipevine Swallowtail caterpillars, which are reddish-brown with rows of fleshy red tubercles rising up from their backs, normally feed in small groups on plants in the pipevine family.  It is these plants that give the insect their poisonous quality.

Pipevine Swallowtail caterpillar

Pipevine Swallowtail chrysalis

Pipevine Swallowtail, Battus philenor

One of our bigger and brighter swallowtails is the Two-tailed Swallowtail (Papilio multicaudata). Growing to over 5 inches wide, their distinctive yellow wings have black tiger-like striping, with a row of bright blue spots along the trailing edge on both sides of the hindwings.  Each hindwing also has two primary black tails, giving this insect its common name.  The Two-tailed Swallowtail caterpillars are carrot-orange with a pair of pale yellow eyespots on top of the head and a pale yellow band behind the head, making them resemble a small snake.  In our area, these caterpillars feed on the leaves of the wafer ash or hop tree.

Two-tailed Swallowtail, Papilio multicaudata

Our largest butterfly is also a swallowtail, is aptly named the Giant Swallowtail (Papilio cresphontes), and can often have a wingspan of over 6 inches.  Their wings are dark brown to black with yellow bands and a yellow spot in the center of each tail on the hindwings.  Their young caterpillars look like bird droppings, which are effective at deterring predators.  Giant Swallowtails have distinctive flight patterns, with the females tending to beat their wings slowly but move quickly over long distances, and the males having a more rapid, jerky flight due to their slightly smaller wings.

Giant Swallowtail, Papilio cresphontes

At times you may find an adult swallowtail butterfly missing some or all of its tails.  While the true purpose of the tail-like extension on the hindwings of these butterflies is unknown, it is often believed that they trick predatory birds into biting off this expendable part of their wing, giving the swallowtail a chance to fly yet another day!    

Dazzling Dragonflies

Halloween Pennant, Celithemis eponina 

With their large, multi-faceted eyes, two pairs of strong, transparent wings, and an elongated body, the dragonfly is an ancient insect that inspires myth and lore in many world cultures.  For Native Americans, their form can represent swiftness and energy, pure water, and even symbolize renewal after a time of great hardship.

Usually found around lakes, ponds, streams, and wetlands, dragonflies typically eat mosquitoes, midges, and other small insects such as flies, bees, and even some butterflies.  They capture their prey by clasping them with their spike-studded legs, and their prey cannot use their usual form of escape by diving away, since dragonflies always attack from underneath!  Normally, dragonflies do not bite humans, but if you grasp one by the abdomen, it will bite in order to escape.

Exuvia of Flame Skimmer, Libellula saturata

The lifecycle of a dragonfly consists of three stages: egg, nymph, and adult.  The female will lay her eggs directly on aquatic plants or merely drop them in water.  Once hatched, these nymphs begin their life living underwater, eating other aquatic creatures.  Nymphs of larger dragonflies will even eat the nymphs of smaller species!  This nymphal stage can last as long as four years in some species, but most overwinter in ponds and marshes and emerge in the spring as adults. Once fully grown, the nymph will crawl out of the water on the stem of a plant, break through its’ skin (called the exuvia) and enlarge its’ body and wings by pumping fluids into them.

Mature dragonflies are known for their aerial acrobatics, capable of hovering and rapid acceleration, and can both hunt and mate on the wing.  They need to make the most of their time as aerial predators, since adults live only up to two months. Adult dragonflies are often confused with damselflies, but they are two distinct insect families.  When at rest, damselflies often hold their wings together or slightly open above their body, whereas most dragonflies hold their wings fully open horizontally or slightly down and forward.  Additionally, the eyes on a damselfly are separated, while the eyes of most dragonflies touch.  

Both damselflies and dragonflies are members of the scientific order Odonata, so their lifecycles are very similar.  The mating behavior of dragonflies is a multi-step process because the male has both a primary and secondary set of genitalia.  He will first transfer sperm from the tip of his abdomen to the secondary structures on his second or third abdominal segment.  Then, using the special structures at the tip of his abdomen, he will grab a receptive female by the eyes (or by the 'neck' behind the eyes if a damselfly).  The pair is now considered to be in 'tandem', and the male tows the female in flight.  To complete the reproductive act, the female bends her abdomen beneath the male and touches the tip to the male's secondary structures.  This position is called the 'copulation wheel' and it is at this point when sperm is transferred to the female to fertilize her eggs.

Roseate Skimmer, Orthemis ferruginea

Dot-winged Baskettail, Epitheca petechialis 

Jade Clubtail, Arigomphus submedianus

Neon Skimmer, Libellula croceipennis

Twelve-spotted Skimmer, Libellula pulchella

The common names for dragonfly species that occur in Texas are as colorful as the insects themselves – Twin-Spotted Spiketail, Roseate Skimmer, Eastern Pondhawk, Black Saddlebags, Blue-Faced Meadowhawk, Halloween Pennant, and Jade Clubtail to name a few.  To some extent, the presence of dragonflies may be taken as an indicator of ecosystem quality.  Local populations and diversity may be strongly affected by changes in water flow, turbidity, and in aquatic or waterside vegetation.  Not surprisingly, the greatest number of species  are found at sites with natural water flows, high water quality, native plants, and a variety of microhabitats.

When you see dragonflies this summer, admire their maneuverability, enjoy their jewel-like colors, appreciate their mosquito-eating, and be thankful that we no longer have the “giant dragonflies” from the Jurassic & Cretaceous geologic periods, when their wingspans were up to six times larger than those we have today!    

A Multitude of Milkweeds

Swamp Milkweed, Asclepias incarnata

Butterfly Milkweed, Asclepias tuberosa

Plants known as milkweeds belong to the genus Asclepias, named after the Greek god of healing, and those known as milkvines belong to the genus Matelea, but both are part of the Dogbane family. Over 40 species of milkweeds and milkvines are native to Texas, and those most notable that are blooming this time of year in Central Texas include Antelopehorns (Asclepias asperula), Texas Milkweed (Asclepias texana), Purple Milkvine (Matelea biflora), and Pearl Milkvine (Matelea reticulata). 

Milkweeds and milkvines are named for their milky juice, which contains alkaloids, latex, and other complex compounds, and some species are known to be toxic. Despite this toxicity, the sap of these plants has been used in many folk remedies, including clotting of small wounds, removal of warts, and as a natural treatment for the undesirable effects of poison ivy. These plants are also an important nectar source for bees and other insects, and are a larval food source for Monarch butterflies and their relatives.

Antelopehorns, Asclepias asperula

Texas Milkweed, Asclepias texana

Forming low clumps 1 to 2 feet across in grassy meadows, Antelopehorns is mostly recognizable by the solitary, rounded arrangement of numerous pale yellowish green flowers at the end of each stem, appearing from March through May.  The leaves are slender and 2 to 6 inches long, often folded lengthwise along the midrib.  Texas Milkweed is a much more upright plant, reaching 6 to 18 inches high, and found on limestone outcrops, hillsides, and in dry fields. Its herbaceous leaves are elliptical and each cluster of white flowers is solitary and forms at the top of branched stems from May to July.  Both of these Asclepias species produce seeds in pod-shaped follicles.  These seeds are arranged in overlapping rows, and have silky filament-like hairs called ‘pappus’ attached to them.  Once the follicles ripen and dry out, they split open and the seeds are carried off by their silken hairs and dispersed by the wind.  

Pearl Milkvine, Matelea reticulata

Plateau Milkvine, Matelea edwardsensis

Usually found in the chalky soils of pastures and open ground, Purple Milkvine is often overlooked and missed.  Its low-growing 2 foot stems radiate from a woody rootstock, and along with its opposite, triangular leaves, are covered with long, spreading hairs.  From April to June, pairs of star-shaped, five-petaled, dark purple flowers rise from the base of the leaves.  A robust, twining vine growing in dry, light shade in thickets on rocky hillsides, Pearl Milkvine is best known for its heart-shaped leaves and flat, green flowers ½ to ¾ of an inch across with pearly, iridescent centers.   These curious flowers have tiny white veins forming an intricate pattern on the surface of the petals, adding to their unusual look.

Milkweeds are a versatile group of plants and are now found in many butterfly gardens.  Studies have shown them to re-grow faster than caterpillars can consume them, allowing the overall plant to continue to survive.  The silk or floss from their follicles have good insulation qualities, even superior to down feathers, and they are now grown commercially as a hypoallergenic filling for pillows.  Even Native Americans have used the nectar from the plant as a source of sweetener, due to its high dextrose content. So, as you can see, there are multiple milkweeds with a multitude of uses!