Archive | August, 2010

Antlion Take Two

30 Aug
An adult antlion (Myrmeleontidae)

An adult antlion perches on a grass stem.

Most people who have heard of antlions think immediately of little sandy pits with jaws lurking at the bottom of them.  As we saw in a previous post, those jaws are attached to a fairly monstrous looking little critter.  But this is just the antlion in its baby form.  Very few people would connect the juvenile to the fluttery damselfly-like adult seen in the picture above.

Antlions, like lacewings, belong to the order Neuroptera (literally “nerve-winged”) so named for the intricate venation of the wings of the adults.  Also like lacewings, both the larvae and the adults are predatory, albeit with very different strategies.  Lacewings are primarily nocturnal, and somewhat weak, fluttery fliers–a trait very different from the fleet agile damselflies they resemble.  However both are ferocious predators in the insect world, despite their delicate appearance.

Close up of an adult antlion held in a hand.

Close up of the head of an adult antlion.

Lacewings can be distinguished from damsel and dragonflies by several characteristics.  Their petal-like wings lack a “nodus” or kink at the top margin that is present in both damsel and dragonflies.  A simpler trait for the layperson is the presence of prominent clubbed antennae.  Damsel and dragonflies have very small, hardly noticeable antennae, whereas owlflies (a close relative of the antlion) have antennae longer than the length of their body.

Like other neuropterans, antlion larvae have large specialized sucking jaws, which they lose in their adult for for more typical mandibles (compare the above and below pictures).

An immature antlion lurking at the bottom of its sand pit.

The head and jaws of an immature antlion are visible lurking at the bottom of its sand pit.

Appropriately, one of the two antlions I was rearing emerged over the weekend so I snapped a photo for you below.  This guys’ a local Texan, the adult of the fellow in the pit above:

Adult antlion (Myrmeleontidae) spreading its wings.

Adult antlion spreading its wings.

Antlions actually make interesting pets.  They can be kept in a dish of deep sand and the only upkeep they require is an ant or other small insect dropped in once or twice a day.  It’s fun to watch their pit building behavior, and you can even keep a few in a large dish and watch them establish territories.  Eventually, they will pupate, weaving their cocoon underground and forming a small ball of sand around themselves.  At this point a perch and a cover of some sort (I used plastic wrap tented over a stick) are necessary to trap the emerging adult and allow it to inflate and dry its wings properly.

Pit Monsters – The Immature Antlion

27 Aug
Antlion Larvae (Myrmeleontidae)

An antlion larvae removed from its pit.

An antlion larvae, viewed up close, is a truly creepy little critter.   It is one of those horror movie-esque predators that makes me very glad I am not insect-sized.  If you remember the pit monster from the original Star Wars movies you have some idea what these guys are all about.  Antlion larvae are famous for the conical pit traps they build to catch their prey.  The antlion larvae finds a fine, sandy soil and moves in backwards circles, burrowing down and flicking sand up to create a funnel above it.  (In fact, pit-building antlions have adapted to a point where they can no longer move forwards.)  The antlion larvae lurks at the base of the pit, ready to grab any small critters that fall down the slippery sides of the pit and become entrapped.  The antlion will also use its head to toss sand at any escaping prey, further collapsing the walls of the pit, and bringing the prey sliding down.

An antlion larvae (Myrmeleontidae) in sand pit.

The head and jaws of an antlion larvae lurking in its sand pit.

Like other members of the order Neuroptera (such as lacewings), antlion larvae have large, distinctive jaws for hooking their prey.  The moving parts of their jaws form two straw-like tubes through which they can inject digestive chemicals and drink their liquefied prey.  Antlions belong to the family Myrmeleontidae (from the Greek words for “ant” and “lion”).  They take their common (and family) name from the large portion of their diet comprised of ants, but they will prey on anything of an appropriate size which stumbles into their grasp.  Although pit building antlion larvae are the best known (and the most easily spotted) only about 40% of antlion larvae actually build pits.  Other antlion larvae employ a wide variety of hunting strategies.  Some lurk just under the soil and rear up to grab unwary passersby.  Other will even emerge and chase down prey above ground.  (And that is not a creature I would want to see running after me.)

Antlion larvae (Myrmeleontidae) with fire ant (Solenopsis invicta).

An antlion larvae catching a fire ant in its pit.

Come back next week to see the adult antlion!

Lacy Wings

23 Aug
Green lacewing on flowers (Chrysopidae).

A green lacewing perches on a flower stem.

I caught this little guy right before he took off from the tip of a flower stem.  Lacewings are members of order Neuroptera,which includes both green and brown lacewings mantispids (mantisflies), and antlions.  Neuroptera means ‘nerve-winged,’ in reference to the intricate venation of the members’ wings.  They are closely related to, and are sometimes classified with, the orders Megaloptera and Raphidioptera, the dobsonflies, fishflies, and serpentflies, all of which also share similarly complex wing venation.

The green lacewing family, Chrysopidae, takes its name from the greek word “chryso” for “gold” for the nearly metallic toned eyes were are often conspicuously golden.  The macrophotography blog Four Ages of the Sand has a gorgeous close up of a lacewing eye. Somewhat like dragonflies, lacewings and other neuropterans are predatory, both as larvae and adults.  Because of this they are popular for pest control, and eggs are often purchased and distributed in large quantities in greenhouses or agricultural fields.  On the other hand, in some situations this same quality may make them a pest insect themselves.  For instance, some scale insects are used for commercial red dyes, and lacewings may prey on farmed populations of these insects.

Home Sweet Home – Carpenter Ants

20 Aug
Carpenter ants (Camponotus) nesting in a catus

Carpenter ants (Camponotus) guard a nest entrance in a prickly pear cactus.

Carpenter ants belong to the ant genus Camponotus.  They take their common name from their nest-building habits.  Most carpenter ants prefer to nest in damp dead wood and will even hollow out dead trees.  As we’ve seen before, however, these ants can also be found in ground nests.  The above ants built a nest in the living flesh of a prickly pear cactus.  I found this group while doing field work in Argentina.  The two workers above did not approve of my nosy camera, and were standing guard over the entrance.

Although carpenter ants do not consume wood like termites do, their nest building habits can make the construction pests if they choose a building wall to tunnel in.

Inching Along – Geometridae

16 Aug
An inchworm (Geometridae) climbing purple flowers.

An inchworm (family Geometridae) climbs flowers at the Welder Wildlife Refuge, in Texas

Inchworms (also called loopers and spanworms) are a type of caterpillar that take their name from their unique method of moving.  Rather than crawl along leg by leg, these caterpillars have adapted to take advantage of the length of their bodies and “inch” along, contracting the front and back portion of their bodies.  Even the placement of the prolegs (false extra appendages found in some insect larvae) has adapted to this behavior–inchworms lack prolegs in the middle of their body.  Inchworms are typically colored in greens or browns to blend into their environment.  Some, such as the caterpillar below, may have extra filaments to aid in their disguise.  Caterpillars may strike poses to resemble twigs, stems, or even bird poop!

An inchworm (Geometridae) takes a cryptic posture on a plant stem.

A filament bearing geometrid on a plant stem (Flynn, TX).

The “inchworm” style of movement has independently evolved in several lineages of caterpillars.  However, by far the most abundant and diverse group are the caterpillars of the geometer moths, in the family Geometridae. This family name literally means “earth measurer” and these moths are often better known for their caterpillars than their adults.

An inchworm (Geometridae) inches along.

Inchworm inching along.


13 Aug
A mosquito fills her belly with a blood meal on an arm.

A mosquito fills her belly with a blood meal.

One weird aspect of becoming an entomologist is that my basic, instinctive reactions to many events has changed.  I’ve mentioned before admiring cockroaches at a restaurant, and  my own particular research has gotten me quite cozy with fire ants.  Apparently, I will also pause to photograph the mosquito sipping blood from my arm as well.  (Bonus oddness:  While I was photographing the mosquito above, a fellow grad student called dibs on it for his collection.)

Mosquitos are flies (order Diptera) belonging to the family Culicidae. The family name is derived from latin ‘culex,’ basically referring to little flying insects  (think ‘midge’ or ‘gnat’).  In their adult form mosquitoes are primarily nectar feeders.  Only female mosquitoes take blood meals, and then only in order to nourish developing eggs.  In the picture above, you can see the fine piercing stylet being used to withdraw blood, as well as the protective sheath which has been folded back in a U-bend.

The mosquito also has the honor of being the first insect I saw on my trip to Argentina last winter.  It was waiting in the rental car for us:

Mosquito (Culicidae) in car window.

Mosquito in car window (Argentina).

This proved to be especially portentous since Argentina was rife with concern over dengue fever, a dangerous mosquito-borne disease that has been making a comeback in the urban centers of Argentina.   The signs we saw most often carried the slogan ‘entre todos contra el dengue’  (all of us against Dengue), and directed people to eliminate standing water (where mosquitoes breed) and be alert for symptoms of the fever.

Posters warning of mosquito-transmitted dengue fever in Argentina.

Posters warning of mosquito-transmitted dengue fever in Argentina.

In fact, the mosquito is the deadliest animal in the world, causing (through the transmittance of disease) more than 2 million human deaths per year.  (Oddly enough, the biggest cause of human deaths by large animal may be the hippopotamus.) Just as diseases can be transmitted from human to human by the use of unsterilized needles, the mosquito’s needle like proboscis can vector diseases from person to person, all without any harm to the mosquito itself.

Mosquito feeding in Argentina

Mosquito feeding in Argentina

The Spider and the Fly

9 Aug
Spider preying on long-legged fly (Dolichopodidae).

A spider preys on a long-legged fly.

Sights like the above are common in sweep nets.  I am always amazed by just how many spiders of all sizes I sweep up in a net, and generally most of them take advantage of the opportunity to grab a fly or other small insect.  Sometimes they even grab another small spider!  Not all spiders use webs to catch their prey–many actively hunt and tackle their prey, bringing them down with a quick venomous bite.  The spider above has grabbed a small0 metallic green fly, specifically a ‘long-legged fly.’

The long-legged flies belong to the fly family Dolichopodidae, from the greek word “dolicho” meaning “long” and “pod” meaning “foot” or “leg.”  (Think of a podiatrist.)  This is a diverse and speciose group, but many members are easy to recognize thanks to their slender bodies, long legs, and frequent metallic coloration.  Interestingly, both the larvae and the adults of this family are predators, hunting and eating other small animals.  In this role they can help to regulate populations of pest species such as mites and tree pests.

Ants and Hoppers

6 Aug
Carpenter ants (Camponotus) tending treehopper nymphs (Membracidae).

Carpenter ants tending hopper nymphs in Argentina.

Since we had the spittlebug nymphs earlier this week, I thought I’d take the opportunity to post a picture of some other hopper nymphs.  These little guys are being watched over by several carpenter ant workers, who will collect their sugary excretions and protect them from predators.

A casual observer might confuse these with mealybugs due to their white, somewhat waxy appearance and their location feeding en masse on a plant stem.  (This casual observer would in no way be me.  Nope.)  However mealybugs, like scales, have reduced appendages and secondarily lost wings.  A close look at these guys will reveal not only well developed legs peeking out, but the presence of small, developing wing buds on their backs, indicating that they are late stage nymphs (immature insects).  In fact, that dark shape near the middle left of the mass appears to be an adult thorn-mimicking treehopper, making it likely that these are members of the auchenorrhynchan family Membracidae.


2 Aug

Spittlebugs (Cercopidae) on a plant stem.

Spittlebug nymphs on a plant stem.

Spittlebugs lay their eggs on plant stems.  The young spittlebugs excrete special fluids which they whip into a foamy mass around themselves (in the above image some of this foam has been wiped away).  This ‘spittle’ serves to protect the nymphs from predators as they develop, feeding on plant fluids.  They grow and molt several times (one of the cast off skins can be observed in the above picture), finally leaving the spittle mass after the last molting into their adult form.  Some predatory insects lurk by spittle masses, patiently awaiting the emergence of the insects.  Spittlebugs may live alone or in groups, and the nymphs sometimes leave their own spittle masses to find a new spot or join other spittle masses.

Spittlebugs (family Cercopidae) are in the hemipteran suborder Auchenorrhyncha, and thus are related to leafhoppers, treehoppers, and even cicadas.  The adult insects resemble broad and stout-bodied leafhoppers, and are sometimes called froghoppers due to their somewhat frog-like appearance.

Close up of spittle bugs.

Close up of spittlebugs.