If you give an ant a cookie…

Pogonomyrmex and Aphaenogaster ants wrestle for a cookie crumb.

At the Southwest Ant Course last summer, I got the chance to participate in some cool biodiversity assays of the local ants, comparing assemblages before and after a flash flood.  Among other things, we pit-trapped, counted nest entrances, and scoured the ground for wandering ants.  To encourage ant activity, quadrants were sprinkled with cookie crumbs.  We were using crumbled up pecan sandies because, and I quote, “those are ants’ favorite cookies.”

I can’t speak for any given ant (I, personally, prefer Thin Mints), but the desert ants of Arizona certainly did seem to like pecan sandies.  I’m also going to go out on a limb and speculate that these cookies are useful as assay tools for their combination of sugars, proteins, and lipids in order to attract ants with a broad variety of diets.

Two different species of desert ants continue to wrestle for a cookie crumb.

Pogonomyrmex (harvester ants) and Aphaenogaster (BugGuide calls these the “spine-waisted ants”) were by far the dominant species in the area.  The ants pictured above wrestling over a cookie crumb were in between two nests, and each was determined to get the prize back to her own colony.  I watched the ants play tug-of-war for several minutes, sometimes even picking up the cookie crumb with the other ant attached (as in the photo above).  Finally, the Aphaenogaster was joined by two of her nestmates, and the out-numbered pogo almost immediately surrendered the prize and fled the scene.  A rousing victory for Aphaenogaster-kind, who I assume went home to celebrate with cookies and tea.

Aphaenogaster ants team up to wrestle a cookie crumb away from a lone Pogonomyrmex ant.

FYI, I believe these were Aphaenogaster albisetosa and Pogonomyrmex maricopa but don’t quote me on that.

Fluourescent Scorpions: Love and Danger in the Dark

Scorpions  at night in the desert, viewed with a blacklight.

One of the coolest night collecting tricks is to take a black light out to look for scorpions.  In the desert (and even in the woods where I live) these cryptic stinging critters emerge at night to hunt, and although they are well camouflaged a simple black light reveals them in glowing color.  There’s a lot of debate about why scorpions fluoresce under ultraviolet light but it may be a further mechanism to help them avoid light (which makes them vulnerable to predators and dehydration).

Scorpions that are not hungry reduce activity on brightly moonlit nights.  Being able to detect and head towards dark areas can also help an organism with relatively poor eyesight to quickly identify refuges such as rocks and bushes (Camp & Gaffin 1999).  Gaffin et al. found that, when blindfolded, scorpions could use their entire exoskeleton as a sensor to detect UV light (2011).  I am now enjoying picturing scorpions in tiny blindfolds.

Two scorpions fighting (or courting?) in the desert at night.

I encountered this particular pair of scorpions in the desert in Arizona.  At first I thought they might be engaged in courtship behavior, but later I thought they might just be fighting (possibly both?).   Yes, I know the pictures look a bit violent with the wrestling and the stinging, but scorpion courtship is, well, probably only fun for scorpions.  I can’t find the excellent clip from Life in the Undergrowth, but there are some lovely videos of scorpion mating dances on Youtube.  For many species, stinging is involved.  Also elaborate dancing, and chewing on each other’s faces (“kissing”).  The courtship is completed when the male manuevers the female backwards onto a spiky spermatophore he has placed on a flat surface.

Two scorpions: fighting or making out?

 

Biting and Stinging: The Ants

A fire ant biting and preparing to sting.

Do ants sting or bite?  I get this question a lot, and the answer I give is: “both–sometimes–it depends.”  This is the kind of helpful answer that makes me near and dear to friends and family.  So let’s break this topic down.

Most ants bite–or in other words they have mandibles (jaws) with which they can grab or pinch objects.  However, many ants are too small to effectively bite humans.  Ants are in the order Hymenoptera, and like their bee and wasp relatives, most female ants have venom and many have a stinger modified from the ovipositor (egg-laying structure).  Thus, many ants both bite and sting.

Close up of a fire ant stinger.

For example, fire ants first bite, grabbing hold with their mandibles, and then sting repeatedly, injecting venom into their victim.  This is why a quick swat at a biting fire ant can often remove them before they sting.  Some very small ants, such as the fire ants’ tiny relatives the thief ants, have stingers too delicate to pierce human skin.  On the other hand, some ants like leaf-cutter ants are so well adapted for biting that they no longer have a stinger.

Leafcutter ant heads used to pinch a cut closed (Photo courtesy P. Lenhart).

However, not all ants with venom have stingers.  Ants make use of a number of structures to spray, wipe, rub or otherwise dispense harmful chemicals.  One prominent example is the formicine ants (Formicinae), a large sub-family of ants which make use of an acidopore to disperse venom.  The acidopore is basically a round nozzle at the tip of the abdomen which ants use to spray formic acid.  Many formicines have a ring of hairs surrounding the acidopore which  can be used to help direct the spray.

The acidopore of Myrmecocystus, a formicine ant.

Spraying formic acid is a very effective technique when used against many other arthropods and small animals, but generally goes completely unnoticed by humans.  However, for the myrmecologist collecting ants with an aspirator, formicines are extremely noticeable, and suction collection is often followed by a cough.  Inhaling formic acid is not fun.

Full shot of the honeypot ant (Myrmecocystus) pictured above.  The curled under abdomen is a typical posture for spraying formic acid.

Giant Jumping Spiders

A large jumping spider from the Arizona desert.

I ran into this lovely individual while attending the Ants of the Southwest course at the Southwestern Research Station in Arizona.  I’ve always had a soft spot for the charismatic jumping spider, and the widespread bold jumping spider –similarly marked in Halloween orange and blacks– is one of my favorites (and one I’ve posted about here before).  The spider pictured here, however, has the distinction of being easily the biggest jumping spider I’ve ever seen.

Paraphidippus basalis jumping spider on a human arm for size reference.

In fact, this individual turns out to be a close cousin to the bold jumping spider, a member of the genus Paraphidippus (“beside Phidippus”) rather than the genus Phidippus.  Other than that, I can’t find much information about P. basalis.  There are pictures of it tagged from Arizona and New Mexico, and Discover Life’s only data point comes from the New Mexico biodiversity collection.  Two people on Bugguide report finding it on agave plants in Arizona (mine was found crossing a trail in the vicinity of agave).

This spider may also look familiar to you for other reasons:  According to Wikipedia, its more common sister species, Paraphidippus aurantius, was the model for the giant mutant spiders that terrorized the Arizona mining town in the humorous horror movie Eight Legged Freaks.

Jumping spider attacks cop car in Eight Legged Freaks (photo via IMDB).

Flying Robot Bugs

House fly at rest.

A house fly takes off vertically into the air.

While snapping pictures of a fly perched beside me during a long car drive I caught a shot of it in mid take-off, as it launched straight up into the air.  I’d never given a lot of thought to house fly flight dynamics before, except perhaps during miserably failed attempts to swat them.  Attempting to learn more on the topic  led me to a fascinating article discussing the use of insects to develop flying nano-robots, aka Micro air vehicles.

Obviously, I want one of these.

A tiny, insect-inspired flying machine (photo: Wood 2008).

But instead of talking about tiny flying robots being harnessed for military purposes I thought I’d tell you some boring fascinating stuff about insect flight muscles.  The oldest insects (Paleoptera: dragonflies, damselflies, and mayflies) have muscles directly attached to the base of the wing (direct flight).  The fore and hind wings are operated independently, allowing for excellent mobility and maneuvering.  All later insects (Neoptera) have muscles that attach to the exoskeleton, and move the wings indirectly by changing the shape of the thorax (indirect flight).  Generally, the wings function together as a single unit.

Because I was bored, I diagrammed the muscles involved in indirect flight:

The dorsoventral muscles contract, pulling down the top of the thorax and causing the wings to rise.

The dorsolongitudinal indirect flight muscles contract, arching the top of the thorax and causing the wings to beat downwards.

If you have trouble visualizing how flexing the exoskeleton in these directions could lead to the appropriate wing movements, I recommend this simple experiment:  Take a tennis ball, and stick two pins in it to represent the wings.  Squeeze the tennis ball from top and bottom (dorsoventral muscles) and from front and back (dorsolongitudinal indirect flight muscles) and observe the movements of the pins.  We did this back in my Insect Physiology class, and it makes for a very striking visual tool.

Wikipedia also has two very useful animations (the direct flight diagrams is mislabeled, though, so mind your links):

• Direct Flight
• Indirect Flight

The flower and the fly

Pretty things.

I’m in the middle of prelims and also a rather prolonged fever but I thought I’d check in before November ended.

Plus now I can stare at this pretty flower and the stripey fly I saw in Argentina.  I don’t know what kind of fly it is but it’s very striking.  Looks like it’s a nectar feeder.  VanEngelsdorp and Mexner recently estimated the global value of insect pollination at US$ 212 billion, or about 10% of the global value of agricultural production (2010).  There, I even included an insect fact.

Shh, only pretty flower-flies now.

*edit* Thanks kindly to Morgan Jackson and Joel Kits in the comments for identifying this as a bee fly (Bombyliidae) in the genus Poecilognathus.  Bee flies are really really cool little flies whose young generally parasitize other insects.

October Taxonomy Fail

No new posts lately because my computer recently came down with a spontaneous and catastrophic case of fail.  I managed to salvage most of my files, but I am still trying to get settled into the new computer and replace various important missing programs, like Word and Photoshop and all programs. Luckily, I am a graduate student, so I have tons of free time and spare cash to dedicate to this task.  (Only one of three statements in that last sentence was true.)

For this month’s Taxonomy Fail, and in honor of Halloween, we have a pretty awesome BBC clip on velvet worms.  I’ve seen this Life in the Undergrowth video about a million times* because we show it to the 201 students and I highly recommend it.  First enjoy the video, then see if you can spot the fail:

(You may need to click over to Youtube to get the video to load properly.)

…Did you catch it?  “This cricket has huge eyes, but it’s difficult to see what’s going on around it.”

At 1:03 (Grasshopper):

Who are you calling a cricket?

At 1:26 (Cricket/Katydid):

I feel like a brand new bug.

Ooooops.

*Where 1 million = 9.

Thrips and other possibly imaginary pains

Close up of a thrips.

While checking out the pecan gall phylloxera from the last post under the scope I observed this little guy exiting the opened gall.  Thrips inquilines have been reported in phylloxera galls, so this may indeed have been a houseguest of the phylloxera colony.

Thrips (awkwardly, this is both the plural and the singular of the word) are exceedingly tiny little insects that are often plant pests as many feed on the mesophyll and epidermal fluid of plants.  Their puncture-style feeding leaves very characteristic spot-like damage on the leaves of plants they feed on.  Because of their small size and ability to tuck themselves into crevices they are often resistant to pesticide applications, particularly those in the form of aerial sprays.  Some thrips may also opportunistically predate on other small arthropods, while some species are exclusive predators.  This also means that when they get into our aphid colony we have to kill everything, bleach the entire room, and start from scratch.  Not that I am bitter.

The order name, Thysanoptera, means “fringe wings” and refers to the unique feathered wings of the thrips.  Although thrips are not strong fliers they are so light that winds can carry them long distances.

Close up of a thrips on a pecan leaf with the fringed wings visible.

Although these guys are quite tiny they also pack a pretty painful bite!  (It’s rather like getting jabbed with a needle.)  Because thrips are so tiny many people never connect them to  that sudden jab of pain apparently from nowhere.  I personally experienced this MANY TIMES in our cotton fields and while assisting my labmate with his thrips colony before anyone enlightened me on the subject.  If you would like to observe your possibly imaginary antagonists you can try this simple trick for collecting them:  In the spring, tap out a flower over a white piece of paper.  Look closely.  Some of the grains of pollen may appear to be moving.  Thrips!

I’m calling these potato monsters

Gall aphid colony in pecan leaf.

I wrote this post up back in the spring, then accidentally deleted it and was too disheartened to come back to it for months.  But these little guys are too cool to abandon forever.  The little yellow potato monsters in the photo above are pecan gall phylloxera, a relative of aphids and thrips.  They are exceedingly tiny.  So tiny that although I observed and curiously popped open the large pecan leaf galls many times while rearing my lunas, it wasn’t until I idly took a look under a scope one day that I even realized the little insects were there.

Open and closed pecan leaf galls with gall phylloxera colony.

Pecan phylloxera have fascinating, complex life cycles.  These vary quite a bit between species, but I’ll share a general example, that of Phylloxera devastatrix, probably the most damaging pecan phylloxera.  Pecan phylloxera galls are started by “stem mothers,” who inject a toxin into the plant while feeding on young tissue.  This toxin stimulates the plant to grow a gall, gradually encasing the feeding insect over the course of several days.  Each stem mother then lays eggs in her gall, which develop and feed in relative safety.  In late summer, at the end of the gall’s life cycle, the galls split open, allowing winged asexual phylloxera to disperse.  They’re not done yet.

Close up of pecan gall phylloxera and eggs.

Not content with such a simplistic, multigenerational life cycle of barely three tiers, the asexual phylloxera find a good spot and lay some eggs.  Two different sizes, just to be more special.  The large eggs hatch into sexual females, and the small eggs into sexual males.  The phylloxera mate, and the mamas-to-be seek out a nice sheltered place…where they die.  This gives the eggs a nice, cozy refuge to ride out the winter–tucked up safe in mom’s dead body.  In the spring, the eggs hatch out of their mother and become stem mothers, which disperse to find young plant tissue and start new galls, beginning the beautiful cycle of life once again.

Damn, I love nature.

More pictures:

Gall phylloxera and eggs in an opened pecan leaf gall.

Close up of pecan leaf gall phylloxera.

Underside and mouthparts of pecan gall phylloxera.

Pecan gall phylloxera nymphs are exceedingly tiny.

References:

Phylloxera gall on Pecan, TAMU

Pecan Phylloxera, Smith & O’Day

Pecan Phylloxera, OK State

Spiders raiding ant nest

Spiders slip inside a sleeping harvester ant nest to prey on the worker ants.

Last week I had the pleasure of attending the new Ants of the Southwest course at the Southwest Research Station in Arizona, and I thought I’d jump right and share with you my favorite entomological encounter.  While black lighting in the desert we happened across a harvester ant nest that was being raided by dozens of small hungry spiders.  The spiders would slip inside the nest entrance individually and emerge some time later, dragging worker ant prey.   It was pretty impressive to watch, particularly as there was no evidence that the spiders’ raiding was provoking any kind of response from the colony.  Harvester ants (or “pogos,” from Pogonomyrmex) are a group of ants with a fairly vicious sting, and the workers dwarfed their tiny spider predators.

I’ve included more pictures as well as a video below, with bonus excited chattering commentary.

A spider drags its harvester ant prey from the sleeping nest.

I don’t have an ID for the spider as of yet.  Several group of spiders are known to mimic ants, either to help them obtain prey or to help them avoid predators.  If these spiders don’t look like ants to you, it’s possible they may smell enough like ants to fool the colony.  Cosmophasis jumping spiders use this scent-disguise tactic to enter weaver ant nests and prey on workers and larvae.  Meanwhile certain spiders in the genus Masoncus take this a step further and live only inside harvester ant nests, where they prey on another nest symbiote, collembolans.

A spider hangs from a grass blade, feeding on a harvester ant many times bigger than itself.

Update:

Thanks for the feedback here and over at Bugguide.  These spiders appear likely to be members of the family Theridiidae and the genus Euryopis.  Many members of this genus appear to be specialist predators of ants.  I poked around in the literature and there are a couple of papers about the species E. coki, a specialist predator of another species of harvester ants, Pogonomyrmex owyheei.  (I believe the harvester ants pictured above were P. maricopa.)  There were a number of similarities to the behavior I observed.  E. coki was observed to lurk outside nest entrances and ambush ant workers, first tacking down a leg with silk and then biting the ant.  When bushes or grasses were nearby the spiders employed a dangling feeding behavior (Porter and Eastman 1982).  Dale Ward has a great shot of a male Euryopis mating with a female spider near the nest entrance of P. rugosus.  Tetramorium’s Ants of Arizona page also has some great shots and info.  I haven’t been able to find any literature on thespiders actually entering the ant nests, though.