Thursday, October 31, 2013

Happy Halloween!

Is your Halloween costume ready?  The females of the dragonfly species known as the "Halloween penant" stay "dressed" in orange and black their entire adult lives.  Yet, they are only likely to be seen on Halloween in the southernmost (and warmest) part of their range -- Florida.

A female Halloween pennant (Celithemis eponina).

Monday, October 28, 2013

Mild and woolly

During a walk through the woods in the fall, it can be tempting to gaze at the trees and their marvelous array of colors, sparing little attention to the ground below.

The woods on a quintessential autumn day.
However, it is still important to look down every once in a while -- and not just to avoid tripping.  Paths through the woods are often shared with animals that are an unfortunate combination of small, slow moving, and easily squished. 

A banded woolly bear caterpillar (Pyrrharctia isabella).
Moreover, while the trees in their autumn foliage emanate a certain serenity, finding a fuzzy caterpillar is much more exciting (at least for me)!  Finding this caterpillar was particularly exciting, as when I got close to see its face...

Facing down the woolly bear. suddenly whipped around into a ball (reminding me of another caterpillar's surprising reaction).

The banded woolly bear in a defensive posture.
Though curling up is unlikely to be a good defense against shoes or wheels, the caterpillar's response did make it easy for me to roll it off the road and out of harm's way.

Tuesday, October 22, 2013

What's that bug? continued

After identifying the lobate lac scale, I thought I would try to identify another of the unusual looking bugs in the "Hemiptera" folder.  The larva pictured below seemed like it ought to be easy to identify due to its distinctive appearance, including branched spikes and secreted covering.

A strange, spiky larva on a leaf.
However, the closer that I looked at the picture, the more I began to doubt that it really was a hemipteran.  But if it wasn't a bug, what was it?  Browsing through the various orders of insects, I stumbled across a picture that looked both strange and familiar -- a match for one of the insects in my "Unknown" folder.

An adult male narrow bark louse (Graphopsocus cruciatus) on a rose hip.
The tiny mystery insect was a narrow bark louse, a distant relative of parasitic lice with a much more agreeable diet of plants, lichens, and fungi.  Returning from this lucky digression to the problem of the spiky larva, I eventually came across a surprising answer.

A tortoise beetle larva with its "fecal shield".
The larva was an immature tortoise beetle and possibly a golden tortoise beetle (Cassida sexpunctata), which is considerably more attractive as an adult.

Friday, October 18, 2013

What's that bug?

While I immediately recognize a few of the arthropods in my photographs, I have to file away many of my pictures for later identification.  Most of these can initially be filed to family or at least order, but a few remain complete mysteries.  The strange, butterfly shaped scale insects pictured below lingered anonymously in my "Hemiptera" folder until I serendipitously came across a similar picture when looking for images of invasive species.

Lobate lac scales (Paratachardina pseudolobata) in South Florida last December.
Further research on the internet confirmed that these scales do belong to an introduced species, the lobate lac scale (Paratachardina pseudolobata).  However, learning more about this insect just raised more mysteries.  Although the lobate lac scale is not thought to be native to Florida (or the Bahamas or Christmas Island, where it is also found), it is not clear where this species came from.  A related species (P. lobata) is known from India and Sri Lanka, so this species is likely to be Asian as well.  The spread of this species -- from wherever its native range is -- is somewhat surprising, given its lack of wings and the fact that adults remain relatively sessile.  Also unusual is the absence of males; unlike its relative P. lobata, this scale reproduces parthenogenetically (asexually), developing from unfertilized eggs.

Explore some more: Featured Creature: lobate lac scale

Monday, October 14, 2013

A problem for roots

The invasive Japanese beetle (Popillia japonica) is notorious for the damage that it causes both above and below ground.  Above ground, adult beetles can be seen voraciously consuming foliage and flowers.  Below ground, beetle larvae feed so extensively on the roots of grasses that conspicuous dead patches form on the lawn above.  However, not all dead patches of grass should be blamed on Japanese beetles; some may be due to another Asian beetle with a large appetite for roots: the oriental beetle (Anomala orientalis).

An oriental beetle (Anomala orientalis) sitting on a daisy.
Like the Japanese beetle, the oriental beetle was also accidentally introduced to North America from Japan in the early 20th century and has been gradually expanding its range.  In contrast to the Japanese beetle, though, adult oriental beetles are not very destructive (I have seen several but never observed one feeding).

Another brown oriental beetle sitting on, but not eating, a fern.
A particularly interestingly aspect of oriental beetles is that they come in several color variations.  Can you spot the slight differences in the patterns of the two beetles above?  I've put a hint below the next picture, which illustrates a more extreme example of color variation.

The less common, black form of the oriental beetle (Anomala orientalis).
Hint: The biggest difference is on the thorax (the segment between the head and the abdomen).  The first beetle has a solid brown patch, whereas the second beetle has a white line dividing the brown patch.  The patterns of white and brown on the elytra (the wing converings on the top of the abdomen) are also not quite the same.  See even more examples on the Natural Current Events Facebook page.

Friday, October 11, 2013

Going for a ride? Take a Beetle or a Vespid!

Since I am sitting in an airport, it seems like a good time to write about travel.  Though insects seem small from our perspective, many of them are able travelers.  They can cover long distances by walking, jumping, swimming, digging, and flying.  Additionally, they can use their sensitive antennae to detect faraway food (such as carrion, in the case of the burying beetle shown below).

A tomentose burying beetle (Nicrophorus tomentosus) attempting to scurry away from the camera.
These characteristics make insects an attractive mode of transport for a group of much less mobile arthropods: mites.  If you look closely at the burying beetle below, you can see the mite that had crawled out from some hidden spot onto one of the beetle's wing covers (elytra).

A mite (Poecilochirus sp.) riding on the back of the tomentose burying beetle.
Poecilochirus mites are commonly found riding on burying beetles, since these mites also need to get to carrion in order to feed.  Some Poecilochirus mites consume fly eggs and larvae on the carrion, while some are predators of the burying beetles' own eggs.  Meanwhile, other mites prefer foods unrelated to carrion and, correspondingly, take different forms of transport in search of those foods.

A group of mites rides on the back of the thorax of a mason wasp (Vespidae).
Are mites at best hitchhikers or free riders?  Perhaps not, as some evidence suggests that insects can benefit from the mites too.

Explore some more: Parasitic mites as part-time bodyguards of a host wasp

Monday, October 7, 2013

More than a pain in the neck, continued

After noticing the pattern in how candy stripe spiders tackle their prey, I decided to look back at my many pictures of crab spiders for comparison.  As I had thought, the crab spiders also frequently bit their prey just behind the head.

A female Misumena vatia crab spider eating a tricolored bumble bee (Bombus ternarius) in 2012.
The crab spiders took a different approach, however, when their prey was a hover fly (Syrphidae). 

A juvenile crab spider eating a hover fly (Syrphidae) in 2012.
In these cases, as illustrated in the pictures above and below, the crab spider bit right into its victim's abdomen.

Another crab spider eating a hover fly, this time on a snapdragon.
In addition to having a soft abdomen, hover flies are relatively easy for crab spiders to catch.  One way for hover flies to compensate for their vulnerability is to spend more time inspecting landing sites for potential danger; indeed, hover flies can often be seen seemingly suspended in the air above flowers before touching down to feed or darting quickly away.

Two hover flies inspecting a flower before landing.

Friday, October 4, 2013

More than a pain in the neck

Since beetles are well defended against spiders by their tough exoskeletons, I was curious how Japanese beetles were falling victim to the candy stripe spiders.  However, each time I found a Japanese beetle and a candy stripe spider together, I had already missed the decisive moment.  Therefore, I was limited to reconstructing events by inspecting the aftermath of the beetle-spider encounters.

A Japanese beetle (Popillia japonica) being eaten by a candy stripe spider (Enoplognatha ovata, ovata color morph).
While watching the spiders consume their prey, I noticed that they were exploiting a weakness in the beetles' defenses.  Like human armor, beetle exoskeletons are vulnerable at the joints.  In the pictures above and below, you can see that each spider has bitten between the beetle's head and its sternum (where the beetle's neck would be if it had one).  Though these spiders had already moved on to feeding, the same spot seems a likely target for the killing bite.

Another Japanese beetle being eaten by a candy stripe spider (Enoplognatha ovata, lineata color morph) in 2012.
Going back through some of my other photographs of the candy stripe spiders, I found that the strategy of "going for the throat" also appears to be effective with other difficult types of prey, such as wasps.

A female candy stripe spider (Enoplognatha ovata, redimita color morph) with a wasp.