Go away or I will glow at you

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.

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.)

Beetles and Parental Care

A bess beetle tends larvae in the interior of a rotting log (Photo courtesy Paul Lenhart).

A few weeks back I did a post on bess beetles, and their fascinating social structure.  These beetles live together in family groups, communicate via an elaborate vocabulary of squeaks, and cooperatively care for the developing brood.  Paul Lenhart recently snagged this awesome photo of an adult beetle with a group of larvae and was kind enough to let me share it with y’all here at 6legs. I thought I’d take the opportunity to do a bit more research and elaborate on what I learned last time.

Initially, a male or female beetle finds a rotting log, and begins hollowing out a tunnel.  Later the beetle will accept a mate, following an elaborate courtship ritual complete with specific acoustical signals.  The mated pair then cooperates on the tunnel and defends it fiercely from intruders.  A clutch of about 30 eggs is laid in a nest of finely ground wood in the tunnel.  When the eggs hatch into larvae, the parents cooperate to feed them specially prepared food–specifically wood which has been pre-chewed, passed as feces, and partially digested by microorganisms.  When the larvae pupate, the adult beetles construct protective pupal cases around them out of wood debris and feces.

Interestingly, young adult beetles cooperate with the parents to help care for their siblings.  The mated pair can have several clutches of eggs over the course of a year, and will often court and mate again in the nest when the initial brood has pupated.  Newly eclosed young adults require several weeks or even months for their adult exoskeletons to fully harden and darken to black.  These young adults are called “teneral” or “red” beetles, and remain in the tunnel, feeding larvae, helping to construct pupal cases, and defending against intruders.  Evidence suggests they may sometimes remain even after reaching full adulthood, assisting their parents and siblings.  Eventually, these beetles migrate from the log to join a mate and start their own family.

(Schuster & Schuster, 1985)

Caterpillar Hunters

Calosoma scrutator, the fiery searcher.

Here’s a colorful beetle I run across fairly often (they are extremely popular in student collections).  While many members of the genus Calosoma, the caterpillar hunters, are black in color, a handful of species (in the creatively named subgenus Calosoma) have metallic green elytra.  Calosoma scrutator, the fiery searchers, are further distinguished by a red/gold band around the edge of the wing cases.  These beetles are fast and aggressive, preying primarily on caterpillars as both adults and larvae.  We recently had a few live beetles donated for an insect zoo we did for a local elementary school, and I got to spend a good deal more time observing them than I ever have in the field.

Caterpillar hunter attacking a cricket.

Not having any caterpillars around, I’ve been feeding them crickets, which they do well on so long as everybody in the tank gets their own cricket meal.  There’s a good deal of scrambling and tussling as each beetle attempts to secure a cricket and retreat to a quiet spot to eat, easily devolving into slapstick if two possessive beetles happen to bump into each other.  I’ve started passing out crickets with tweezers to minimize the chaos.  Luckily, they all appear to be too armored to take any real damage from each other, and they haven’t shown any inclination to eat each other–though at least one forum thread I found says they may.  When not eating or searching about the tank they spend most of their time burrowing or tucked under bits of wood and debris.

Nom nom.

Caterpillar hunters possess a ferocious pair of mandibles, but don’t appear to be particularly adept at manipulating their struggling prey–unlike spiders with their pedipalps or mantises with their raptorial forelegs.  Instead they scissor away at the soft fleshy parts of their prey, slowly masticating it into a pulp.  I have some rather alarmingly gory video that I’ll try to get up at some point.

Apparently the adults have been known to live for an impressive three years, so I’ll have to see if I can keep these flashy fellows around.

Nom nom nom

Nooooooooo (Attack of the Carpet Beetles)

Bee fly with eyes eaten out by dermestids.

Here’s a sight no insect collector wants to encounter in the collection boxes.  I was sorting a mixed box of pinned specimens when I found that this fuzzy bee-mimicking fly had met a second untimely fate  (the first being the fate that led him to be pinned in my collection).  As you can see, the large bulbous eyes that occupy most of the bee fly’s head are, um, no longer occupying.  In fact, they’ve been rather neatly eaten away.  Apparently, bee fly eyes are delicious.

Dermestid damage in an insect collection.

With mounting horror I sifted through the collection box and found all the signs: tattered insects, scattered frass, and (the smoking gun) cast off larval skins.  One hairy skin stuck to the wing of a tiger moth whose hollowed out abdomen had apparently made a tasty treat.

Cast off exoskeleton of a carpet beetle larva (Dermestidae).

Dermestids.  Oh, joy.  Is there any insect that is more unwelcome in an insect collection?  (Actually, my friend Paul had an unpleasant experience with a voracious colony of fire ants, but that’s another story.)  These guys, often called carpet beetles or hide beetles, are dietary specialists on dry, high-protein organic materials.  Everything from dandruff to leather to natural fiber carpeting may become their food source.

Carpet beetle close up (80 times magnification).

This not only makes these beetles a damaging household pest, it makes them both dangerous and very useful to to people who work with dead things.  When they’re not uninvited guests, dermestid beetles are frequently used to “clean” skeletons, removing hide, flesh, and all.  If you’ve every watched the show Bones, you may be familiar with Zack’s colony of “flesh-eating” beetles kept for this purpose.  (Zack: You can’t kill them.  They have names.)

The scaled exoskeleton of a varied carpet beetle (Anthrenus verbasci).

These particular guys were varied carpet beetles, a fairly common indoor pest.  Examining them under a scope reveals that these tiny, nondescript little blobs are quite striking.  The beetles are covered with tiny, multi-colored scales in orange and white and black and their rotund little bodies, with legs retracting into grooves, mak them look something like carnival balloons.  Pretty adorable for something that can leave a trail of carnage and destruction in its wake.

The legs of the carpet beetle can tuck back into grooves.

Luckily, the damage was fairly limited (the two specimens pictured here were by far the worst off) so I can consider the whole incident with amusement and interest.  The pictures were fun.  The collection?  Is cycling through the freezer.  Only dead bugs welcome in these boxes.

Pointed carpet beetle with hand for scale. (Thanks to Loriann Garcia for providing the pointed specimen for the impromptu photo shoot.)

—

A/N:

Can we talk for a minute about the fact that I took all these pictures with my cell phone?  Forget hoverboards; we are living in the future.  Right now.

It would never have occurred to me to point an iPhone down a dissecting scope without Alex Wild’s recent post over at Myrmecos.  Clearly, I had tons of fun with this.  I highly recommend it.

Squeaky Beetles

Bess beetle (Passalidae) on decaying wood.

My labmate Paul brought me a box of bess beetles (family Passalidae) left over from a live insect lab.  I love these little squeakers, so I was pretty pleased.  I am not the only one who thinks the beetles are adorable.  BugGuide attributes the common name “bess beetle” to the French word baiser, “to kiss,” apparently due to the squeaky “kiss” noise these beetles make when disturbed.  This stridulation is produced by rubbing the top of the abdomen against the hind wings.  In fact, bess beetles produce at least fourteen distinct acoustic signals (Schuster 1983), giving them a pretty complex repertoire for an insect.

Less cute story:  when I was a kid, my brothers and I caught one of these for somebody’s science class.  We put it in a jar with some acetone and had to take it out again because it sounded like it was screaming.  (Anybody seen the Fly?)  Now that I’ve shared that adorable story, let me go back to talking about my awesome new pets.

Bess beetle chewing dead wood.

Bess beetles employ a fairly elaborate vocabulary because these beetles are subsocial.  Adults excavate galleries in the dark recesses of rotting wood where they live together in family groups, cooperatively caring for their brood.  Larvae are fed pre-chewed wood by the adults.

There’s an extra twist.  Unlike termites, bess beetles don’t have endosymbionts in their guts to digest wood for them.  Instead, they process the wood and excrete it, wait for microflora to further digest the wood, and then eat it again.  (Rabbits, as ruminants, employ a similar “eat it twice” tactic.  If I have destroyed your image of bunnies, I apologize.)  Both adults and larvae starve if they are not allowed feces as part of their diet.  Yum yum!

Two Weevils

A small black weevil feeds on a flower.

For a long time the extent of my knowledge about weevils was that joke.  You know the one.  (Or possibly you don’t.  My dad has a terrible addiction to bad puns.)  My mental conception of weevils was ‘some kind of buggy thing that gets in food.’  But now, as an entomologist, I know that they are a type of beetle thingy that gets in food.  And, you know, other stuff.   Weevils (and snout beetles) belong to the family Curculionidae, from the latin Curculio or “corn worm.”  I just think of curlicues.  With more than 40,000 species, weevils are the largest family of beetles, while beetles themselves are the most speciose order in Animalia.  Basically, this means there may be more species of weevils than any other animal on Earth.*

*Conceptions of species distributions are a rapidly changing field, and one strongly influenced by both ability and motivation to identify cryptic species.  For example, the wasp family Ichneumonidae currently has about 15,000 described species but estimates place the actual species count as high as 60,000. (Townes 1969)

A weevil (Curculionidae) on a fingertip.

Whatever the case, it is clear that this group has been very successful.  Why?  How about the advantage of a novel adaptation?  Most weevils are characterized by a unique, snout-like beak.  Despite appearances, this is not a piercing-sucking mouthpart.  Instead, the chewing mandibles are placed at the end of a long, tubular beak which gives them the reach to bore in to fruit, seeds, flowers, trees, etc.  Of course, a long snout like that requires other adaptations.  For one thing, most weevils have elbowed antennae that can fold back into a groove on the snout while feeding.  (For an example check out Ted MacRae’s excellent pictures.)  Another contributor to their success?  Well, as stored products pest these guys are extremely hardy.  We have a glass jar of corn and weevils that we use as part of our live insect display at outreach exhibit.  It has not been opened in years.  The corn is mostly powder but the beetles are chugging along.  Go weevils!

Scarabs: The Green June Beetle

A green june beetle (Scarabaeidae: Cotinis).

Here’s a beetle that my dog, a budding canine entomologist, chased down and caught for me on our walk the other day. These big, metallic green beetles are one of the more striking insects we see in the area.  This fellow was out a bit late in the year, so it was fun to see one.

Much like the brown june beetles (or “junebugs”) that mob my porch in the summer, adult green june beetles are attracted to lights.  The adults feed on fruit and sometimes flowers (they are a significant vineyard pest), while the grubs shelter in the soil during the day and emerge at night to feed on vegetation and roots (they can be a minor lawn pest).  Apparently these grubs have the unique habit of crawling on their backs, using short stiff hairs rather than their legs, which is a cool fact I did not know.  Two characters of note for this genus are the horn-like projection of the mouthparts and the way in which the pronotum (first plate of the back) extends to a point, covering the scutellum.

As a side note, it is extremely difficult to capture metallic and iridescent coloration on camera (I lack the appropriate combination of equipment, patience, and skill).  Ted MacRae of Beetles in the Bush has some good comments on the subject, and just generally takes gorgeous tiger beetle photos.

Taxonomy Fail: When is a roach not a roach?

A polyphaga cockroach, labeled with a photo of a darkling beetle.

I found these ‘Real Bugs’ lucite-encased specimens for sale a local grocery store.  They’re pretty nice display items, and I’m actually kind of in love with the included collector’s cards which include trivia along the lines of “millipedes can have thousands of legs.”  Above you can see the polyphaga cockroach, whose trading card inexplicably showcases a photo of a darkling beetle.  Quick, someone calculate the taxonomy fail index.

I also love that they’ve not only hyped up the cards with “speed,” “size,” and “gross factor” ratings, but also “DEADLINESS.”  This is kind of vaguely plausible for the centipede and “giant bee,” but what about the long-horned beetle? (Deadliness: THREE.)  Frankly, I can’t wait to get my hands on the whole set.

Bleeding Blister Beetles

A disturbed blister beetle (Meloidae) bleeds a defensive skin irritant and toxin from its leg joints. (Photo by Paul Lenhart)

Here’s a fantastic shot of  a blister beetle showing off its name sake (Thanks to Paul for the picture!).  When handled or otherwise disturbed (such as by a hungry predator) beetles in the family Meloidae secrete hemolymph, the insect equivalent to blood, from their joints.  In the above picture you can see the drops of yellow fluid at the beetle’s “knees.”  The hemolymph contains a toxin called cantharidin, which can cause skin irritation and blistering in humans and can be fatal to ingest.  Basically, they bleed poison.

The fellow above is male, as recognizable by the antennal kinks.  These kinks are used by males during courtship to entwine with the female’s antennae (someone blogged about this recently with excellent pictures, but I can seem to find the post*).  Only the male beetles produce cantharidin, but they pass it along to females as an extra benefit to mating.  Among blister beetles cantharidin actually functions as a female attractant.  Cantharidin extracts from blister beetles are used medically to remove warts and even tattoos.  Horses are particularly sensitive to cantharidin, and cantharidin toxicosis, caused by ingestion of alfalfa or hay products contaminated with blister beetles, can cause symptoms varying from “depression to severe shock to death.”

*Edit:  Found it!  TGIQ wins about a million points for the phrase ‘antennal foreplay.’

Life Cycle – Red-headed Chrysomela leaf beetle

A red-headed Chrysomela leaf beetle (Chrysomela texana).

These  red-headed Chrysomela leaf beetles were all over the park near my home this week, mostly in the vicinity of a large willow tree, the beetles’ food of choice.  Chrysomela texana are close relatives of the cottonwood leaf beetle (Chrysomela scripta).   C. texana can be easily distinguished by it’s red pronotum, head, and underside (most similar species have distinct black markings on these areas).  Every life stage of the beetle was apparent, from the yellow eggs laid in clusters on a leaf, to the lady beetle-like black and brown larvae, skeletonizing the surrounding vegetation in gregarious clusters, the red-brown pupae.

A cluster of yellow red-headed Chrysomela leaf beetle eggs on the underside of a leaf.

(Note: The egg hunt was successful.  Happy Easter!)

A gregarious cluster of red-headed Chrysomela leaf beetle larvae skeletonize a willow leaf.

Like swallowtail caterpillars, the larvae have cool, eversible glands which they use to secrete defensive chemicals (as pictured by Mike Quinn on BugGuide).  The pupae of these beetles were particularly abundant.  They seemed to be stuck to every surface I looked at–tucked under bark, into crevices, dangling from leaves and even from small flowers and weeds.  This gave me the chance to snap the pictures below of a beetle struggling out of its pupal case. I even took a few home, but they were sneaky and eclosed on me when I wasn’t looking.

A red-headed Chrysomela leaf beetle (Chrysomela texana) ecloses from its pupal case.

A red-headed Chrysomela leaf-beetle ecloses from its pupal case.

Cast off pupal case of a red-headed Chrysomela leaf beetle.

*edit*

Surprise bonus image!  Now the life cycle is complete. 😉

A mating pair of red-headed Chrysomela leaf beetles (Chrysomela texana).