American Cockroaches

28 Feb

blattidae_american_cockroach_side_view

I sat in on a introductory entomology lecture about cockroaches this week, so this seemed like a good topic.  Above you see my least favorite insect and also my frequent friend and visitor for night time assays in the greenhouse this past summer, the American cockroach.

I like this picture because it shows off a lot of great cockroach adaptations: the flattened body for fitting through tight spaces, the head tucked defensively under the pronotum, with the eyes wrapped around the top of the head for good vision in this postion, the long delicate antennae for sense perception in the dark, and the cursorial legs for running at high speeds.

My feelings about cockroaches have evolved since I entered entomology, and while I still don’t welcome them in my house, I now consider them fairly interesting to observe in other places and I even keep a small colony of hissers.  I think I crossed a hurdle while I was desperately collecting insects for my class collection during my own introductory grad student course.  After months I had somehow managed not to encounter a single cockroach of any species, which left me down an entire order.  When I finally saw one of these large ladies scurrying across a pavilion floor I jumped on it with my bare hands.  (In terms of weird cockroach collecting methods this still does not top the dinner doggy bag incident.)

Go away or I will glow at you

7 Feb
Glow in the dark Elateridae: Pyrophorus

Pyrophorus sp. click beetle collected in Argentina. (aka Deilelater sp.)

Here’s a cool beetle I found a while back, all the way down in Argentina.  This is a member of the family Elateridae, the click beetles, so named for their snapping/jumping defense mechanism.  Click beetles are cool enough that I really ought to give them their own post, but for now I’ll just direct you to Ted McRae’s recent excellent post on the subject.  There are tons of species of click beetles, all pretty easily identifiable by their elongate shape, back pointed pronotum, and the mesosternal spine they use to go click.

This particular click beetle has an extra trick up its sleeve.

Luminescent, phosphorescent click beetle

Pyrophorus sp. click beetle with glowing eye spots on pronotum.

The glowing click beetles are a genus (recently revised into several genera) notable for the two glow-in-the-dark spots on their pronotum.  Several species are native to the Southern US.  In researching these beetles I find a mixed bag of explanations for why they glow.  The adult beetles bioluminesce at night, and this light, which can vary in color from species to species, is involved in species-specific recognition cues in mating, much like fireflies (Feder & Valez 2009).

The eyespots also brighten when the beetles are startled, suggesting a warning, anti-predator function.  Facultative aposematism (warning colorations that are only sometimes used) can be especially useful when an organism has different categories of predators, some of which will find it distasteful and learn to respond to warning coloration and some of which will not (Sivinski 1981).

Finally, both the larvae and the adult beetles bioluminesce and the light may also function as an attractant for small insect prey, particularly for the larvae.  (My source for this last bit is Wikipedia.  Make of that what you will.)

The beautiful beautiful hairy maggot blowflies

10 Jan
Pair of iridescent green and blue hairy maggot blow flies with red eyes.

A pair of hairy maggot blow flies.

I posted a while back on maggot art as an outreach activity, and in that post I made the claim that adult hairy maggot blowflies are quite lovely.  My friend (and forensic entomologist) Meaghan Pimsler has come to the rescue, providing a gorgeous set of photos in defense of this claim.  She was also kind enough to give me some additional information on the biology of these interesting flies.

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Chrysomya rufifacies, the hairy maggot blowfly is invasive in the US, and native to the pan-Asian region.  They are of interest to forensic entomologists partly because the young maggots are predators and cannibals.  The adult flies often lay their eggs on carcasses with fly eggs of other species so that their offspring can feed on the other maggots.  Not only does this set up some interesting ecological interactions between the invasive species and native flies, but the patterns of colonization of various flies help forensic entomologists to determine time of death for corpses.

A red-eyed green and blue slightly fuzzy blow fly (Calliphoridae).

Iridescent green-blue-gold coloration of the adult hairy maggot blow fly.

 Interestingly, these flies have monogenic sex determination, meaning that each female will lay only male or only female offspring.  Also, hairy maggot blowflies are not very cold tolerant, and so each year they start out confined to the southern US states, and then successive waves colonize farther north.  They can reach as far as Canada before it gets too cold for them.
Close up of the red eyes and mouthparts of a blue green Chrysomya rufifacies fly.

Who could say no to this cute face?

On a less attractive note, in Australia and Thailand, where these flies are considered native, they have been recorded to cause myiasis in both humans and animals.  Myiasis is a really lovely (I’m just kidding; it’s gross) parasitic infection wherein fly larvae develop in the tissue of a living mammal.  In the case of humans and flies, this is most likely to mean maggots infesting a open wound, although a few types of flies (most famously the botfly) can burrow into unbroken skin and develop under the surface.

Courtship mating interaractions of blow flies (Calliphoridae)

A group of hairy maggot blow flies viewed under a scope.

Thanks again to Meaghan for pics and info!

Do fire ants cause weddings?

6 Sep

aka the “Correlation is not Causation” post

chart via Google Correlate

Google search activity for “fire ant” and “wedding gift” show a strong correlation.  (via Google Correlate)

While playing with Google Correlate recently, I discovered that lots of people tend to search for the term “fire ant” at the same times when lots of people search for the term “wedding gift.”  In fact, with regards to being the search term most strongly correlated with “fire ant,” searches for a “wedding gift” rank second only to searches for “fly traps.”  (I am uncertain if this latter represents an urgent need for pest control solutions or carnivorous plants, but I wish people luck in their quest.)

What does this mean?  Do fire ant stings somehow induce people with a desire to form government-recognized pair bonds, or at least acquire gifts for such events?  Does the proliferation of wedding cake cause outbreaks of ravenous stinging ant populations?  Could the fire ants themselves be the ones searching for the perfect, tiny wedding gift?

Or, more likely, does this correlation highlight the strongly seasonal nature of both these phenomena?  I’ll let you judge that for yourself and also tell you that the answer is that last one.  In fact, fluctuations in fire ant and wedding gift searches are more likely affected by fluctuations in temperatures, weather, and times that are convenient to fly in-laws across the country.  These similar direct causes (with the exception of vacation time and airfare, which fire ants tend not to worry about) probably lead to the indirect correlations.  This is a fun reminder that establishing causality can be challenging, and statistics must be interpreted with care.

Judging by the graph of search activity, the need to deal with both weddings and pesky fire ants peaks in summer months and tapers off sharply in the cold of winter, when presumably both ants and prospective happy couples go dormant for the winter.

Other notable seasonal search terms that correlate with “fire ants”:

“Wedding gift” on the other hand tends to correlate extremely strongly with terms involving golf, for reasons I will leave to some other scientist to explore.

When is a fly not a fly?

5 Jul
wingles army ant symbiote myrmecophile commensal

A wingless phorid fly from an army ant raiding column under magnification.

Here’s a pretty cool little critter.  This strange-looking bug is actually a wingless phorid fly that we captured running in a column of army ants in Arizona.  Army ants are somewhat famous for hosting a wide variety of myrmecophiles.

Line of marching ants.

A raiding trail of army ants.

June Morphology Fail

28 Jun

Here’s another Taxonomy Morphology Fail for your edification and/or entertainment.  See if you can spot this one.

I present:

Pedipalps are not, as it would happen, gonads.  In male spiders these modified mouthparts* are sometimes called “boxing gloves.”  While they are used to transfer sperm from the male spider’s reproductive organs to the female’s, they are not in any way involved with sperm production.

I would expand upon the boxing glove sperm delivery analogy but it gets unsettlingly pornographic very quickly.

via Discovery News

*To be more accurate pedipalps are probably homologous to crustaceans’ second pair of antennae.

Life of a carpenter ant

24 Jun
Camponotus brood - larva, pupa, cocoon

Carpenter ant pupa cocoon and first instar larvae.

Ants, like butterflies, are holometabolous and go through complete metamorphosis with an egg, a larva (~caterpillar), a pupa (~chrysalis/cocoon), and adult ant (~butterfly).  In ants, the larvae resemble small white grubs and cannot move by themselves–they are fed and tended by the worker ants.

Newly hatched ant larvae in brood pile.

Carpenter ant first instar larvae viewed under magnification.

The larvae are covered in fine hairs which help them stick together in clumps, making it easier for adult workers to move and tend them.  In fire ants, these hairs also help with rafting behavior, because they can trap a layer of oxygen around the larvae, helping them breathe and making them extra buoyant.  Rafting fire ant colonies use their babies as tiny floatation devices.  Please take a moment to consider the wonder of nature.

As they grow, the larvae molt several times, and each growth stage is referred to as an instar.  The larvae pictured above are extremely tiny because they are first instar larvae, having only recently hatched.

Inside an ant pupal cocoon.

A pupating carpenter ant larva after spinning her cocoon.

When the larvae are old enough they prepare to metamorphose into adults.  Some ants, like these carpenter ants, spin themselves into cocoons to pupate, while others, like fire ants, leave their pupae exposed.  Above, you can see an opened cocoon that contains a larvae that has not yet molted into its pupal form.

Additional fun fact: ant larvae have a closed digestive tract (I assume to prevent them from making a mess all over the colony.  It’s like the ant equivalent of diapers.). They poop for the first time when they molt into pupae.  Best line from a paper ever:  “…the larva defecates for the first time…. Workers help out.” (Taber, 2000).  This is also the least appealing job description.

An opened ant pupa cocoon.

A carpenter ant pupa in her opened cocoon.

While the job of the larva is eating and growing, the job of the pupa is developing–reorganizing its system into an adult ant.  Ant pupa look basically like unmoving, pale adult ants, darkening up right before their final molt to adulthood.  The newly molted ants are still fairly pale and soft-bodied.  They are referred to as “callows.”  Their exoskeleton darkens as it hardens, until they are prepared to go about the daily business of an adult worker ant.

Magnified camponotus ant.

Adult carpenter ant worker.

PS:  Here is a cool video of a queen ant helping a pupa shed its old larval skin.

Pseudoscorpions

31 May
Pseudoscorpion.

Pseudoscorpion.

Here’s a tiny little predator I picked out of a leaf litter sample.  Pseudoscorpions are another cool bug that I had no idea existed until I started studying entomology.  These charming little arachnids are named for their resemblance to tiny, stingless scorpions.  At only a few millimeters in size, they prey on other small organisms such as insect larvae, mites, ants, and lice.  Although fairly common and widespread, they often go unnoticed.  (When found they are sometimes mistaken for ticks or small spiders.)

A tiny pseudoscorpion perched on a finger.

A tiny pseudoscorpion checks its claws.

Like scorpions, the front ‘claws’ of the pseudoscorpion are derived from the pedipalps (a type of mouthpart). Although they lack a stinger, most pseudoscorpions have a venom gland and duct in their pincers instead, which they use to immobilize their prey.  (Their claws are too small to enable them to sting humans.)  They then digest their prey externally by pouring digestive fluids over their captive in a method similar to spiders.  Like spiders, pseudoscorpions have spinnerets and can spin silk to construct shelters.

Pseudoscorpion perched on a finger.

Pseudoscorpion perched on a finger.

Sources and additional reading:

May Taxonomy Fail: Insect Tattoos

24 May
insect tattoo art book

And when they say “insect” they mean…

It’s been a while since I’ve posted a good taxonomy/morphology fail.  This one’s got a little of both.

A friend gave me this wonderful little booklet of temporary “insect tattoos” a few months back, and my fellow entomology graduate students and I had a lot of fun picking out which tattoo best suited each of us.

As you can see from the cover, this collection played fast and loose with the definition of “insect.”  (Wait, scorpions are insects, right?)

Something is awry with this spider.

Something is awry with this spider.

My personal favorite was the tarantula.  At least, I’m assuming that’s what it was.  You can see the artist has made the common mistake of counting the pedipalps (essentially a leggy sort of mouthpart) as a pair of legs.  This would-be arachnid has, not eight, but six legs.   It seemed appropriate.

As an alternative theory, perhaps they were trying a little too hard to fit the spider into the “insect tattoo” classification.

I wore it with pride.

I wore it with pride.

 

Fighting ants and Freeloading flies

17 May
Harvester ants fighting chopped in half on a rock

Harvester ants fight while a freeloader fly awaits the spoils of war.

I snapped this picture of fighting harvester ants in Arizona, and it wasn’t until I could see the images under the camera’s magnification that I was able to notice a few cool details.  First, please note that this is not in fact, two harvester ants fighting, but rather two and a half ants fighting.  These ladies are tenacious in battle.  Second, as I glanced through the series of pictures of this encounter I realized that one of the ants had a passenger.  (Or, perhaps, was showing off her lovely living hat.)  Paul Lenhart clued me in to the really interesting bit of biology playing out here.

Fighting ants and fly

Harvester ant tug-of-war, with freeloader fly looking on.

The fly riding out the fight atop one of the ants’ heads belongs to the family Milichiidae, the freeloader flies.  These very small flies are best known for the members of the family which make their living as commensals or kleptoparasites of predatory insects.  The adult flies hang out near predators, such as spiders or assassin bugs, and sometimes even ride along with them (attendance) awaiting the opportunity to sip up fluids exuded by wounded prey.

Harvester ants fighting and wrestling

Freeloader fly rides out a fierce ant tussle.

Much like mosquitoes and blood-feeding, in many species only the female exhibits this parasitic behavior, presumably because she needs a high protein diet to lay her eggs.  Some myrmecophilous species (ant-loving) have developed such a specialized relationship they even directly solicit ants for food via regurgitation or have larvae tended by worker ants in the nest.  In some cases this interaction takes the form of a “mugging.”  The flies pursue an ant, and, if they can successfully grab hold of the head by gripping the end of the antennae, the ant will then freeze and the fly can extend its proboscis into the ant’s mouth and trigger the regurgitation reflex (Wild & Brake, 2009).  As always, Alex’s pictures are impressive, so if you can’t access the paper figures definitely check the subset in his gallery.

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