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Showing posts with label Travis County. Show all posts
Showing posts with label Travis County. Show all posts

Friday, January 29, 2021

A Water Dance of Grebes

Eared Grebe in winter plumage, lacking the characteristic and showy golden ‘ear’ feathers.

Winter is one of the best times to observe waterfowl in central Texas. Several species spend the colder months on our quiet lakes, reservoirs, and ponds, searching for food in the open, unfrozen waters.  One interesting family that can be seen this time of year are the grebes, aquatic diving birds known for their strong swimming, but not often seen on land or in flight.

Grebes are not ducks, although both are considered to be waterfowl.  They lack webbed feet like ducks, and instead have lobed toes.  Their legs attach further back on their bodies than ducks, making it supremely awkward for them to walk on land. Combined with their lobed toes, however, these attributes make them powerful swimmers and divers for their size.  In our area, there are three species of grebe that can be observed, the Pied-billed Grebe (Podilymbus podiceps), the Least Grebe (Tachybaptus dominicus), and the Eared Grebe (Podiceps nigricollis).

Pied-billed Grebe

The Pied-billed Grebe is a small but chunky waterbird 13.5 inches long that is brownish overall with a blocky head, short thick bill, and almost no tail.  During breeding season, its pale bill has a vertical black stripe, which gives it its name as ‘pied’ means having two or more different colors.  These grebes can trap water in their feathers, giving them control over their buoyancy, sinking deeply or exposing as much or as little of their body as they wish. The Pied-billed Grebe is present year-round, but are more abundant from mid-September to mid-May.  They are not gregarious, so they are often solitary or found in very small groups.

Least Grebe

Least Grebes arrive in central Texas in mid-September, but become scarce by early February.  As the smallest grebe in North America at 9.75 inches long, they have golden yellow eyes, a slim dark bill, are purplish gray in summer, and overall gray brown with a whitish throat and paler bill in winter.  Rather uncommon or local, they can sometimes hide by submerging their entire body under water with only their bill visible.  The Least Grebe is light and has large wings relative to its size, so it can take flight from the water more easily than most other grebe species.

Unlike the previous two grebes, the Eared Grebe is the most abundant grebe species in the world, but it is largely a winter resident in Texas, typically appearing by October and disappearing by May.  It is also a small waterbird at 12.5 inches in length with a bright red eye, very thin bill, and overall dusky brown with white.  In their summer range further north and west, they are black with chestnut sides, and sport golden ‘ears’ or wispy feathers that fan out noticeably from their cheeks behind their eyes. Eared Grebes migrate only at night, and their southward migration in the fall is the latest of any bird species in North America.

The collective noun for a group of grebes is a ‘water dance’, which refers to the fact that they have some of the most elaborate courtship displays of all birds.  Often described as ballet-like, these displays can include bowing, feather fluffing, and rising up nearly out of the water, extending their necks and appearing to run across the water’s surface.  Displays vary and can occur between mated pairs or two competing males, suggesting that they have multiple functions.

Get out this winter and scan the open waters for these beautiful little birds.  While they are not particularly common, nor do we normally see them in the height of their breeding plumage, they are still standouts among the typical rafts of ducks that overwinter in our area. 

Tuesday, December 1, 2020

Frost Flowers


Blooming from August to November, Frostweed provides late season nectar
and a unique surprise at the first frost.

Accompanying the crunching of fallen leaves and the rattling of seed pods drying in the breeze is the arrival of the first frost.  This marks the seasonal change from our relatively warm autumn to the cooler days of a mild central Texas winter.  How does frost, this sparkling layer that sometimes covers the fall landscape, form? 

When the temperature of the air reaches a point where the water vapor in it can condense out into water, it is called the dew point.  The frost point is when the dew point falls below freezing, and rather than producing dew, it creates frost.  Consisting of tiny, spike-like crystal structures called spicules that grow out from a solid surface, frost generally forms on surfaces that are colder than the surrounding air.  Even the size of the crystals can vary, depending upon the amount of time they took to grow, the relative changes in temperature, and the amount of water vapor available. 

A frost flower.

Cold air is denser than warm air, so quite often lower areas become colder on calm nights due to differences in elevation.  Known as surface temperature inversion, this phenomenon forms ‘frost pockets’ or areas where frost forms first, due to cold air trapped against the ground.  It is here, in these areas, that you can find a rare and wonderful spectacle of nature called ‘frost flowers.’

While many plants can be damaged or killed by freezing temperatures or frost, this varies by the type of plant and tissue exposed to these conditions.  In central Texas, there is a common plant called Frostweed (Verbesina virginica), which is found in low-lying areas near streams, creeks, canyon bottoms, and in dappled shade at woodland edges. 

Bordered Patch

Silvery Checkerspot

Much of the year, Frostweed goes unnoticed while it grows 5 to 8 feet tall and leafy, the top of each stalk crowned by a cluster of small white flowers.  Its stalks are oddly square-like, with fleshy green flanges. Frostweed begins to bloom in the August heat, and continues until first frost, well into the fall.  These flowers provide late-season nectar for many insects, including bees, beetles, flies, wasps, and even migrating hummingbirds and Monarch butterflies.  It is also a host plant for Silvery Checkerspot and Bordered Patch butterflies.

A patch of frost flowers.

With the first frost, however, the water contained in each Frostweed plant stem expands, causing the stems to crack.  Via capillary action, more water is drawn through the cracks, freezes when it hits the cold air, and forms long curls of ice like petals of a flower, ribbons, or other delicate, abstract sculptures.  Most often, they consist of longitudinal bands of fine ice threads at right angles to the stem.  These delicate flowers of the frost are fleeting in nature, and can only be found in early morning, as the rising temperature quickly melts them away. 

A prime example of crystallofolia.

Only a few species of plants exhibit this unique phenomenon, which has been called ‘crystallofolia’ by Bob Harmes at the University of Texas, from the Latin crystallus or ‘ice’ and folium or ‘leaf’.  Much is left to be discovered reading the purpose of this process, but further research by Dr. James Carter at Illinois State University has concluded that the ice formation often far exceeds the amount of moisture locally available within the plant’s stem, so it must be augmented by water drawn up from the roots.

Delicate curls can form when more plant moisture is available.

On the surface, fall may seem as if nature is shutting down for the winter, but take the time for a second look and you just might be surprised.  The first frost of the season is another intriguing part of the ongoing cycle of life and renewal for our native plants and animals.

Friday, May 15, 2020

Quercus with a Purpose

All oaks, like this Post Oak, are members of the genus Quercus.
Texas is home to dozens of native species of oaks, all of which are in the genus Quercus.  These trees provide humans with ample shade in the summer and beautiful color in the fall, and they sustain many mammals and birds with their acorn fruit.  But did you know that they are native host plants for dozens of butterflies and moth species, or the plants the female adults lay their eggs on for their caterpillars to eat?  In turn, the caterpillars of these butterfly and moth species provide a critical food source for almost all of the songbirds raising broods in the spring. Three of the most productive native oak species in central Texas are the Texas Live Oak (Quercus fusiformis), Post Oak (Quercus stellata), and Bur Oak (Quercus macrocarpa).

Texas Live Oak
The Texas Live Oak is also known as Escarpment Live Oak, Hill Country, and Plateau Live Oak.  Considered a semi-evergreen tree, the previous year’s leaves fall from the tree only when pushed out by newly emerging ones in early spring.  It has a stately mature form and unparalleled longevity, reaching to 40 feet in height with large limbs that over time spread an appreciable distance from the main trunk.  Firm textured leaves are oval to elliptical, 1 to 3 inches long, with young leaves having pointed lobes.  Its acorns are spindle-shaped or fusiform, narrowed at the base and ¾ to 1 inch long.  

Juvenal's Duskywing
Grote's Buckmoth
The Texas Live Oak is a host plant for Oak Hairstreak (Northern form), Juvenal’s Duskywing, and Meridian Duskywing butterflies, as well as Grote’s Buckmoth, Eastern Buckmoth, and Delilah Underwing moths.

Post Oak
Also known Iron Oak and Cross Oak, Post Oak is a deciduous oak to 50 feet, coarsely-branched with a dense, oval crown.  Its leaves are typically 3 to 5 inches long, with 4 pairs of lobes on each side, and the upper pair are often larger than the others, resembling a cross.  Acorns are ¾ to 1.25 inches long.  Post Oak is the most common oak throughout Texas, and its hard or iron wood is used for railroad ties as well as construction posts and timbers.  

'Northern' Oak Hairstreak
Polyphemus Moth
It is a host plant for the Oak Hairstreak (Northern form) and White M Hairstreak butterflies, and the Polyphemus, Eastern Buckmoth, Scarlet Underwing, and Little Nymph Underwing moths.

Bur Oak Acorn
Bur Oak is one of our largest oaks, also known as Savanna Oak, Overcup Oak, Prairie Oak, and Mossy-cup Oak.  A deciduous tree that can exceed 100 feet in height, its massive trunk supports heavy, horizontal limbs and lobed leaves up to 9 inches long.  Its acorns are the largest of all native oaks, up to 1.5 inches wide, with much of the acorn enclosed in a coarsely scaled cup with a heavily fringed margin. Sometimes spelled Burr Oak, it is the northern most oak in the New World, extending farther north than any other oak species.  

Banded Hairstreak 
Imperial Moth
Bur Oak is the host plant for the Banded Hairstreak and Juvenal’s Duskywing butterflies, in addition to the Ilia Underwing, Imperial, and Greater Oak Dagger moths.

While Texas is known for its oaks, care must be taken in identifying and maintaining oak trees.  Most all of the species can hybridize, occasionally making exact identification difficult,  and several of them are susceptible to oak wilt disease. However, they are worth the effort from a human and wildlife standpoint, as they are Quercus with a purpose!


Sunday, April 5, 2020

Blue Beauties

Blue Curls, Phacelia congesta
Spring brings a festival of color to our landscape in the form of wildflowers, mostly in shades of red, yellow, orange, purple, pink, and white.  But the most infrequent color of them all is blue.  There is no true blue pigment in plants, so they don’t have a direct way to produce blue color.  Plants have to perform a sort of trickery to produce blue blooms, using a common plant pigment called anthocyanin.  Plants have evolved to tweak their normally red to purple anthocyanin pigments by naturally modifying pH and then mixing those pigments, and combined with the way natural light reflects, these factors result in the creation of blue flowers.

Dayflower, Commelina erecta
Aside from the well-known bluebonnet, there are other blue beauties in bloom this time of year, including Dayflower (Commelina erecta), Blue Curls (Phacelia congesta), and Texas Bluestar (Amsonia ciliata).  Dayflower is a 3-foot high perennial with soft jointed stems that grow upright only if supported by other plants.  It blooms from May to October, but most frequently in spring or fall. The flowers are about 1 inch across, with two larger showy blue petals and one much smaller white petal.  Lasting only a day, several of these ephemeral blooms occur on one plant, generally one at a time, each opening 3 to 4 days apart.  Often found growing in dry scrub and partly shaded woods, its other common names include Widow’s Tears and White-mouth Dayflower.

Blue Curls, also known as Caterpillars, Fiddleneck, or Spike Phacelia, is a leafy annual or biennial that grows 1 to 3 feet tall in sandy or rocky soil.  Its periwinkle blue, bell-shaped flowers are ¼ inch long and occur in numerous slender, coiled clusters that uncurl as the buds develop, resembling the suckered underside of an octopus tentacle.  Its leaves are soft and deeply cut, often appearing ragged, borne on a brittle stem.  Blooming from March to May, Blue Curls is often found in large colonies in meadows and woodland edges.

Texas Bluestar, Amsonia ciliata
Growing up to 2 feet tall, Texas Bluestar blooms from March to June in dry open woods and on chalky hills.  Its narrow almost needle-like leaves occur singly but close together all long the stem up to the flower cluster.  Every cluster is made up of few to numerous pale blue flowers, each ½ inch long and wide, with a narrow tube opening into 5 petal-like lobes shaped like a star, with a ring of white at the center.  It is also known as Fringed Bluestar, referring to the fringe of small hairs found on the new leaves and plant stems. 

Less than 10 percent of the more than 280,000 species of flowering plants on Earth produce blue flowers.  Interestingly, while blue did not develop as a common color during the process of natural selection, plants that have blue blooms don’t seem to deter beneficial pollinators.  Both birds and insects can widely detect blue wavelengths, and blue flowers are just as capable of producing food as flowers of other colors. 


Thursday, November 7, 2019

Gone to Seed


The seed heads of Illinois Bundleflower (Desmanthus illinoensis)
contain nutritious seeds that are the favorite of Bobwhite Quail.


Often used as an informal figure of speech meaning to deteriorate or go downhill, ‘gone to seed’ can have a negative connotation.  But each seed contains a new beginning: a tiny plant just waiting for the right conditions such as water, warmth, and a good location, to germinate and grow.  Seeds and seed heads form fascinating shapes, varying sizes, and intricate patterns, often adorning the fall and winter landscape.

Texas Star or Lindheimer Daisy (Lindheimera texana) has a five-pointed
seed head in the shape of a star. 

Plants have many ways of dispersing their seeds, and most have evolved over millions of years.  While many of the methods are tried and true, certain seeds have developed in very particular ways to take advantage of such methods, and some plants only release their seeds in response to specific triggers. 

The feathery seed heads of Scarlet Clematis
resemble small galaxies.

Wind helps seeds float or flutter away, often aided by seed structures such as thin wing extensions or long, feathery tails like those on the endemic Scarlet Clematis (Clematis texensis).  Texas Bluebonnets (Lupinus sp.) employ the expulsion or explosion method, where the small, pebble-like seeds are forcibly expelled when the dried pods twist open in the warm sun.  Similarly, Flame Acanthus (Anisacanthus quadrifidus var. wrightii) has hood-shaped capsules enclosing seeds attached to a hooked stalk, ejecting the seed from the capsule when it dries and breaks open. 

The hood-shaped seed capsule of Flame Acanthus.

Gravity plays a part in many plants seed dispersals, where weighty seeds fall off the plant and roll to a new location.  The best example of this are the round, heavy fruits that simply fall off a plant when ripe, such as those on Mexican Plum (Prunus mexicana) or Texas Persimmon (Diospyros texana).  If the fruits have a tough outer shell, they may travel some distance from the parent plant, and if they have a soft skin, they may break open where they fall and scatter the seed or seeds within.  

Mexican plums are a favorite food of wildlife.

Some plants produce very light seeds, seeds with buoyant fluff, or seeds with air trapped in them, so they can float away from the parent plant that grows in or around water, like Common Buttonbush (Cephalanthus occidentalis) or Black Willow (Salix nigra) or Eastern Cottonwood (Populus deltoides).  Others employ the assistance of animals, which can come in the form of seed or fruit eating (where the seed can pass undigested through the animal), seed caching or burying, or seed transportation. Common examples of seed and fruit eating include Cedar Waxwings and American Robins consuming juniper and yaupon berries, and seed burying is a common practice of both ground and tree squirrels, who eat and cache acorns. Often unbeknownst to the animal, some seeds can be covered with tiny hooks or spines that catch on a passing animal’s fur, eventually transported to and rubbed off in another location. 

The cottony seeds of an Eastern Cottonwood.
This fall and winter, let the seeds linger, at least until early spring. Not only do they provide much needed food for wildlife, but leaving them allows for some beautiful and mysterious patterns in your winter landscape, and the promise of renewing the cycle of life that begins again each spring!


Thursday, October 3, 2019

Night Bloomers

Berlandier's Trumpets
Many night blooming flowers have white or light-colored blossoms, a strong fragrance (although not always to human noses), and open by night and close by day.  These flowers are extremely important nectar sources for pollinators, and they are attracted to these flowers’ nectar mainly by scent.  Two of our best night blooming native plants are Berlandier’s Trumpets (Acleisanthes obtusa) and Jimsonweed (Datura wrightii).

Closeup of Berlandier's Trumpets
Also known as Vine Four O’Clock, Berlandier’s Trumpets is an upright perennial herb or climbing vine up to 6 feet long, easily controlled but often clambering over shrubs and small trees if left unchecked.  Its opposite, bright green leaves are triangular shaped, about 1.5 inches long, with slightly wavy edges.  But it is its white to light pink trumpet-shaped flowers, about 2 inches long, that bloom from April to December, producing a fragrant scent when open at night.  Berlandier’s Trumpet does well in full sun to part shade, is drought tolerant, and easy to grow and maintain.

Jimsonweed
Jimsonweed is a 3 to 6 foot tall stoutly branched herb, with alternate, coarse, large gray-green leaves that are broad at the base and pointed at the tip.  While its foliage is often described as rank-smelling, its flowers are sweetly fragrant white trumpets, up to 8 inches long, sometimes tinged with purple at the edges.  It blooms from May to November, and its flowers open in evening and close during the heat of the day.  

Jimsonweed Bloom

The fruit of this plant is a very distinctive spiny, globular capsule up to 1.5 inches in diameter, which opens fully when ripe.  Jimsonweed has several other common names such as Sacred Thorn-apple, Angel Trumpet, Devil’s Trumpet, and Sacred Datura. Some of these names refer to its use as a hallucinogen in Native American ceremonies, but it is important to note that all parts of this plant are toxic to humans.

Jimsonweed Fruit
Both of these native night blooming species attract several species of Sphinx moths (sometimes known as hawkmoths or hummingbird moths) as well as other pollinating insects such as long-tongued bees, butterflies, and hummingbirds.  But it is the Jimsonweed that has mastered the art of mutualism, with its partner the Carolina Sphinx.  

Carolina Sphinx
While it is common for this plant to benefit from its relationship with the Carolina Sphinx (Manduca sexta) in the form of pollination, in turn it provides nectar for the adult moth and is the host plant for the moth’s caterpillars.  These large caterpillars (known to gardeners as ‘tomato hornworms’), consume many or all of the Jimsonweed’s leaves. But the plant is prepared for the attack, storing resources in its massive root enabling it to produce more leaves for the next generation of caterpillars.  In effect, Jimsonweed grows its own pollinators to ensure its reproductive success!

Thursday, September 5, 2019

Aquatic Apalones

Spiny Softshell Turtle
The genus Apalone is thought to come from the Greek apo meaning ‘separate’ and the Anglo-Saxon alone meaning ‘solitary’, as well as the  Greek apalos meaning ‘soft’ or ‘tender.’  All of these terms apply to the members of this genus, which is comprised of the softshell turtles native to North America.  Turtles of this genus exhibit marked sexual dimorphism, or the condition where the two sexes of the same species exhibit different characteristics beyond their sexual organs.

Females grow to twice the size of males, in terms of carapace or shell length.  In males, the claws on their front feet are longer than those on the back feet, enabling them to better hold on to the female while mating.  In females, the claws on the back are longer, for digging into sandbanks in order to lay her eggs.  Lastly, males have a thicker, stout tail that extends well beyond the edge of its carapace, but the female’s tail is relatively thin and barely extends beyond the carapace.  From a behavioral standpoint, the female is much more solitary, wanders more, and requires deeper water, while the male often congregates with juveniles in sandy shallows and while basking along exposed banks.

Spiny Softshell Turtle
There are two species of softshell turtle in Texas. The more common Spiny Softshell Turtle (Apalone spinifera) is found throughout the state, while the Smooth Softshell Turtle (Apalone mutica) is found only in parts of the eastern two-thirds of the state. The Spiny Softshell’s olive-gray or tan carapace is leathery and flat, and has small spines along the front edge, which explains its species name.  At home in rivers, lakes, ponds, and other bodies of water with muddy or soft bottoms, its spends its time feeding on aquatic insects, fish, and crayfish, basking or floating at the surface, or buried in soft, shallow substrates.  Its long neck and snorkel-like nose allows the turtle to breathe at the water’s surface without having to leave its buried location. Females typically grow to 22 inches, while males top out at 8.5 inches in length.

Smooth Softshell Turtle
The Smooth Softshell’s olive-gray to brown carapace is also leathery and flat, but lacks any spines, bumps, or projections.  This characteristic is reflected in its species name, which means ‘shortened’ or ‘docked.’  It also prefers bodies of water with soft, sandy bottoms, and basks on banks, logs, rocks, or under shallow water with its long nose exposed.  Primarily insectivorous, it will also consume vegetation and small invertebrates and fish.  Smaller than the Spiny Softshell, females grow to 14 inches and males to 7 inches in length.

One odd but amazing fact about softshell turtles is that they are believed to absorb 70% of their oxygen through their skin.  The other 30% comes from pumping water in and out of their pharynx or throats, which contain many tiny projections of tissue with small blood vessels that provide a huge surface area for oxygen absorption.  This adaptation allows them to remain underwater for several hours.  Now that’s one highly aquatic Apalone!


Tuesday, August 6, 2019

A Different Kind of Longhorn

Cottonwood Borer

The Cerambycidae are a family of longhorn beetles, typically characterized by extremely long antennae, often as long as or longer than the beetle’s body.  Also called longicorns, over 400 species have been described in Texas alone.  The scientific name of this beetle family is named after the shepherd Cerambus, a mythical Greek figure who was transformed into a large beetle with horns after an argument with nymphs.  Most of these beetles can fly well and are found on tree trunks, logs, flowers, or come to lights at night.  Some even squeak as a defense mechanism when held, making a rocking motion with their head which rubs tiny ridges against the inside surface of their thorax.

Cottonwood Borer
Two of our more common longhorn beetles are the Cottonwood Borer (Plectrodera scalator) and the Long-jawed or Horse-bean Longhorn Beetle (Trachyderes mandibularis).  The Cottonwood Borer is one of the largest insects in North America, reaching 1.6 inches in length and 0.5 inches in width.  It has a bold black and white pattern on its body with long black antennae.  The white portions of the pattern are actually microscopic masses of hair.  Adults are active by day, feeding on leaf stems and shoots of cottonwood trees.  The female bores small holes in the base of the tree to lay her eggs.  The larvae take up to 2 years to mature, then they pupate for about 3 weeks in a root below ground, and once metamorphosis is completed they chew their way out of the root and dig their way to the surface.

Long-jawed Longhorn Beetle
Long-jawed Longhorn Beetle has a glossy black or dark brown body with 4 generally large but sometimes reduced yellow to yellow-orange markings, and segments of its antennae and legs alternating between black and yellow-orange.  It can grow to a length of 1.3 inches, and is generally common from March to November.  Its species name comes from the fact that the males have much expanded jaws or mandibles. Active during the day, adults are mostly found near wounded trees as they feed on oozing sap, and its larvae feed on native hackberries as well as non-native ficus and tamarisk species.

Goes fisheri
One of the subfamilies of the Long-horned Beetles is the Lamiinae, or Flat-faced Longhorns.  This includes the 9 New World species in the Goes genus, one of which is rare and endemic to Central Texas.  This species, Goes fisheri, was first described in 1941, but does not have a common name.  Beetles in this genus are typically twig girdlers or stem borers, although the food plant of G. fisheri is currently unknown.  It is distinguished from a more common species, G. pulcher, or the Hickory Borer, by the grayish pubescence of its elytra or wing covers.  G. fisheri is just over 1 inch long, not including its antenna, appears to be nocturnal in its habits, and is attracted to artificial light. 

This large family of longhorns includes beetles called sawyers, pruners, and girdlers in addition to borers.  Most are found in dead or dying wood, and some mine live plants.  While many of these beetles are considered to be occasional pests, it should be noted that they literally help shape the forest canopy and assist in recycling dead wood into precious soil.  All the more reason to appreciate this different kind of longhorn!

Saturday, June 29, 2019

Some Like It Hot

Eastern Ringtails, a type of Clubtail, obelisking.
The dog days of summer are upon us, and a long stretch of sultry weather lies ahead.  It can be a challenging time for people and for wildlife, but for some, it is their chance to put on a show. 

Bouquets of Mountain Pinks
Mountain Pink close up
Mountain Pink (Zeltnera beyrichii), also called Meadow Pink, Catchfly, or Quinineweed, is an annual herb less than a foot tall and best described as a neat bouquet of small, pink flowers.  Blooming May through July, Mountain Pink sprouts up like an inverted cone 8 to 12 inches high, on hot, rocky hillsides, limestone outcrops, and along gravelly roadways.  Its leaves are threadlike and are held below the multiple 0.5 to 1.0 inch wide showy pink five-petaled blooms that provide nectar for moths, butterflies, bees, and other insects.

Woolly Ironweed
Woolly Ironweed (Vernonia lindheimeri) is a 10 to 30 inch high clumping perennial, with woolly gray stems and long, narrow leaves.  Its bright purple flowers lack true petals, but the disk flowers are arranged in showy, terminal clusters.  A well-behaved species that should be used more often in gardens and landscapes, Woolly Ironweed blooms from June to September, and prefers open hillsides, roadsides, and fields offering full sun.  It is a good nectar source for many species of butterflies during the heat of summer, and is highly deer-resistant.

Blue Dasher, a type of Skimmer, obelisking
To prevent overheating on hot, summer days, some dragonflies and damselflies assume a handstand-like position called ‘obelisking.’  They raise their abdomens until the tip points up toward the sun, which helps to minimize the surface area of their body that is exposed to solar radiation.  Both males and females of these species will raise their abdomens when the temperature is high, and lower them again if shaded. Laboratory experiments have shown that this behavior is effective in stopping or slowing the rise in their body temperature.  This method of thermoregulation is practiced by about 30 different species in the Skimmer, Clubtail, and Broadwing Damsel families.  All are considered ‘perchers’ or sit-and-wait predators that spend a considerable amount of time stationary.

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.’  Many common species of cicadas in North America are in the genus Megatibicen  and are generally called the annual or ‘dog-day’ cicadas because they emerge every year in July and August, the dog days of summer.

Resh Cicada, Megatibicen resh
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.

Even in the heat of a long Texas summer, nature is busy going about its mysterious ways, offering sights and sounds that can recalibrate our senses, and allow us to continue to appreciate all that it has to offer.

Monday, June 3, 2019

Mariposa de la Muerte


Commonly known as owlet moths, cutworms, or armyworms, moths in the Noctuidae family make up one of the largest families of Lepidoptera.  The word Noctuidae is derived from the Latin word noctua meaning ‘little owl’ and the largest moth in this family in the continental United States is the Black Witch (Ascalapha odorata).

The Black Witch moth has been known as mariposa de la muerte or ‘butterfly of death’ since the time of the Aztecs, when it was believed that they were harbingers of death.  With a wingspan of up to 6 inches, its upperside is mottled dark brown to grayish-brown with hints of iridescent purple and pink, and females, which are slightly larger and lighter in color than males, have a pale almost lavender-pink median band through both fore and hind wings.  

A Black Witch (male) attracted to our mercury vapor light
Common to abundant in the New World topics as far south as Brazil, the Black Witch flies year-round in south Florida and the Rio Grande Valley of Texas.  In June and July, summer monsoons in Mexico trigger this fabulous creature to migrate north through Texas, where it is often found roosting in garages, under eaves, or under bridges.  It has the ability to migrate great distances over bodies of open water, such as the Gulf of Mexico, and one specimen was recorded in 1903 in Leadville, Colorado, caught in a snowstorm on the Fourth of July!

Primarily nocturnal, the adult Black Witch is attracted to light and fermenting fruit.  Its larvae feed at night on a variety of cassias, acacias, ebony, mesquite, and other woody legumes, and rest during the day hidden under bark and branches.  Up to 3 inches long, its caterpillar is dark gray tinged with brown, with a pale stripe down the back and dark stripes down the sides, and it relies on this natural camouflage to make it difficult to spot.  Pupation occurs on the ground in scattered leaf litter within a fragile cocoon.  Black Witches breed year round in overlapping generations, and their adult stage is thought to last only three or four weeks.

A Black Witch (female) perched above our front door!
At first glance, this very large moth is often mistaken for a small bat hovering around a porch light, but it will eventually land and linger for several hours if undisturbed.  If this happens to you, you can only hope that the South Texas legend of the Black Witch is true, as it states, “If a Black Witch lands above your door and stays there for a while, you could win the lottery!”