Archive | September, 2010

Cute Bug? Ladybug Life Stages

29 Sep
Ladybug on a leaf (Coccinellidae)

Cute ladybug on a leaf (Coccinellidae).

This is a special retroactive emergency update post in honor of my mother’s birthday.  Apparently I don’t post enough ‘cute’ bug pictures.  (I think they’re all cute, but that’s just me.)  Ladybugs have been demanded and will be supplied.

Pupa of a ladybug.

Pupa of a ladybug.

This is a somewhat less cute picture of a ladybug pupa.  This is the ladybug equivalent of a chrysalis or cocoon.  It is an inactive, resting life stage while the ladybug restructures its body into it’s adult form.  The ladybug’s aposematic coloration which warns that it is toxic to eat allows it to pupate exposed on the leaves of plants in the midst of its primary food source–aphids.  Many other beetles pupate underground, inside plants, or drop to the leaf litter at the base of trees to pupate.

Cannibal ladybug larva (Coccinellidae).

Cannibal ladybug larva.

And finally a picture of a ‘baby’ ladybug.  Awwww.  I had to look closely to figure out what was going on in this picture.  At first I thought it was a ladybug larva molting out of its previous skin, but in fact this larva is apparently cannibalizing another ladybug larva.  Delicious!

Happy birthday, Mom!

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Predator or Prey

27 Sep
A leaf-footed bug nymph (Coreidae).

A leaf-footed bug nymph in profile (Coreidae).

Look at the picture above and the one below.  You may notice a resemblance to some of the insects I’ve talked about in my most recent posts.  However, despite their similar appearance these bugs are actually two different types of insects from two very different families.  The insect above is an herbivorous leaf-footed bug (Coreidae), while the bug below is a carnivorous assassin bug (Reduviidae).  In fact, many leaf-footed bugs and assassin bugs in the field bear a striking resemblance to each other.

Assassin bug peering over a leaf (Reduviidae).

Assassin bug peering over a leaf (Reduviidae). The stridulatory groove can be observed on the prosternum.

How to tell them apart?  Those same sucking mouthparts that classify them both as hemipterans.   These beaks, or rostrums, may both be designed for sucking fluids but they also tell us something about the kind of food each bug eats.  Leaf-footed bugs, and other coreids are exclusively plant eaters.  Assassin bugs and other reduviids are exclusively predators.  As a rule of thumb, the beaks of herbivorous insects are longer than those of carnivores.  This is because most herbivorous insects need to pierce deep down into the tissue of plants to reach the sticky sap.  Predatory insects, on the other hand, have short stabbing knives of beaks to quickly pierce their prey and inject toxic digestive chemicals.

As you can see, the leaf-footed bug in the first picture has a beak reach most of the way down it’s body.  The beak of the assassin bug in the second picture is much shorter.  In fact, among reduviids this beak is the most diagnostic trait for identification.  The beaks of reduviids tuck under their heads and fit into a small notch in their sternum, or chest, called a stridulatory groove.  Reduviids can rub their beaks across the rough surface inside this groove to  create a rasping noise (stridulation) to warn off predators.

The Assassin (Bug)

24 Sep
A colorful assassin bug.

A colorful assassin bug (Reduviidae, Lick Creek Park).

Here’s a pretty little bug I’ve run into a number of places.  This is an assassin bug, a member of the family Reduviidae (which also includes the ambush bugs).  This diverse family of bugs take their name from their predatory habits.  They use their short sharp sucking mouthparts to stab their prey and inject lethal digestive chemicals which liquefies the prey’s internal structures.  In fact, although they are not particularly aggressive, many species can deliver a painful bite to humans if molested. One family, the aptly named kissing bugs, even makes a habit of biting humans in soft fleshy bits such as the lips to sip their blood.

A ventral view of the bee killer assassin bug.

A ventral view of the bee killer assassin bug (Reduviidae, Welder Wildlife Refuge).

This particular species of assassin bug, Apiomerus spissipes, is also called the bee assassin or bee killer, for its tendency to prey on bees and other pollinators as they visit flowers.  It is fairly widespread across the southern United States and among the more colorful and strikingly patterned of the assassin bugs.

Leaf-footed Bugs

20 Sep
Leaf-footed bugs and nymphs feeding on a thistle.

An aggregation of leaf-footed bugs and nymphs feeding on a thistle.

I found these adult and immature leaf-footed bugs congregating on a tasty thistle in a local park.  The bright orange coloration of the nymphs warns predators that they might not enjoy the taste of the little guys.  The adult bugs have another defense.  Like stinkbugs, they have two thoracic scent glands, and can put out quite a strong, sickly sweet odor when disturbed.

Leaf-footed bugs belong to the family Coreidae. As you might guess, they take their common name from the leaf-like extensions on their hind tibiae.  This family also includes members without such ornaments, collectively referred to as squash bugs.  Leaf-footed bugs are ‘true bugs’ in the order Hemiptera and suborder Heteroptera. Like other hemipterans, they have sucking mouthparts, which coreids use exclusively for feeding on plant fluids.  Adults in this group range in size from fairly small (1-2 cm)  to some of the largest terrestrial bugs (over 1 inch), and can be quite impressive.

Fuzzy Wuzzy Was A (Wooly) Bear

17 Sep
A tiger moth caterpillar (Arctiidae) climbs a grass stem.

A tiger moth caterpillar climbs a grass stem.

When I was little I was always taught not to touch caterpillars because they might sting.   ‘Especially the fuzzy ones.’   This training has survived in me and even today I am leery of the fuzzy variety of caterpillars, despite knowing that the stinging caterpillars are vastly in the minority and fairly distinctive.  Luckily, friend and caterpillar expert Laura Ann was with me when I encountered this particular fuzzy fellow in the Welder Wildlife Refuge, so I not only had the opportunity to pet the little guy, but to try him out as a mustache and unibrow.  He was a bit too active for either post.  “Arctiids are fast,” Laura Ann pointed out helpfully, as my temporary unibrow made its escape.

Tiger Moth Caterpillar - Arctiidae

A fuzzy black tiger moth caterpillar.

Tiger moths, family Arctiidae, take their name from the pattern common on many members’ wings, which often includes orange and black markings on a white background.  These are relatively common visitors to light sheets here in Texas.  Their caterpillars are often fuzzy, giving them the common name “wooly bears” or “wooly worms.”  Like other caterpillars, its prolegs (the additional pseudo-legs it has as a larvae) are equipped with one or two rows of tiny curved hooks called crochets (see prolegs on the picture above).  The hooks allow them to climb smooth surfaces like plant stems and leaves.  The patterns and placement of these hooks are used for identifying many immature Lepidoptera.

Luminescent

13 Sep
A luna moth (Saturniidae) with wings lit from behind.

A luna moth (Actias luna) with wings lit from behind.

We set up a light sheet in Sam Houston Park early this spring, and were positively swarmed with dozens and dozens of luna moths.  In person, I found these moths to be somewhat less graceful than certain sleep aid commercials have led me to believe.  They arrived in the area of the light sheet in a commotion of wings, and fluttered around bouncing noisily off everything in the vicinity before dropping to the ground.  Occasionally, they managed to cling to someone’s hair or shirt like a colorful decoration.  However, whatever they lack in grace (at least around lighted obstacles) they make up for in impressive size and striking coloration.

These large, charismatic moths are well known but rarely seen, as populations reach adulthood and mate only once or twice a year, and the moths hide away during the day.  Luna moths live only a brief time in their adult form, about a week, and their delicate wings quickly become tattered.  Like other saturniid moths, they don’t feed as adults, and lack the coiled tube mouthparts of other butterflies and moths.    Moths in the family Saturniidae are easily recognized by their large size; stout, fuzzy bodies; absent mouth parts; and broad wings.  They also generally have large feathery (plumose) antennae, which assist them in tracking down mates.

A luna moth (Saturniidae) on the leaf litter.

A luna moth (Actias luna) on the leaf litter.

Extra Extra – Embioptera, the Webspinners

10 Sep
Winged adult male webspinner (Embioptera)

Adult male webspinner (Embioptera)

So I have a story to tell about the picture above.  See, that guy up there is a webspinner, a member of the order Embioptera, a fascinating but often overlooked little group of insects.  I spent most of last spring looking for a webspinner because these guys were worth super-extra bonus points for our class collection.  I peeled bark off trees.  I journeyed to a location where one of my undergraduate students had stumbled across one.  Twice.  But no luck.

Then, a few nights ago, I was sitting at home, reading a book and minding my own business, and an embiopteran fluttered up and landed on my nose.  Life is strange.

Luckily, my entomologist instincts are well-honed enough at this point that I reacted to the sudden presence of an unknown insect on my face by attempting to determine what it was.  I then had a few frantic excited moments of “catch it! catch it!” before I secured my prize:  an adult male webspinner.

Webspinner (Embioptera) in spun silk tube.

Webspinner in silk gallery.

Webspinners, as I have mentioned, are members of the order Embioptera, meaning “lively winged.”  No one seems to agree quite why this is, though a few sources suggest this is in reference to the ‘lively fluttering of the males’ wings.’  Webspinners take their common name from their living habits.  They spin silken tubes, called galleries, in which they reside most of their lives (males may leave their tubes to seek a mate).  Often they form their galleries in large communities, under bark or rocks.  They have several very interesting adaptations for this lifestyle.  Most notably, they have special silk making gland in the enlarged segments at the base of their swollen fore-tarsi (in essence, their front feet–see the first picture).  Although all insects make silk at some point in their lives, they are the only insects to have glands in their feet.

Male webspinner (Embioptera) in silk gallery with wings partly folded back.

The wings of a webspinner folding backwards at the blood sinuses.

Webspinners are also adapted to move about in their silken tubes.  They have long slender bodies, and can move rapidly backwards and forwards.  Their large hind femurs (essentially their hind thighs) assist in backwards movement, and the two sensitive filaments at the end of their abdomen (cerci) allow them to feel their way along the tunnel backwards.  In addition, females are wingless, somewhat resembling earwigs.  Adult males, like many insects, need wings to fly and search out females.  Thus, male webspinners  have a special adaptation to keep their wings from hindering them in the tunnels:  their wings are soft and floppy, folding forwards for backwards movement.  In order to provide the stiffness necessary for flight some wing veins are adapted into blood sinuses, and can be pumped full of hemolymph to stiffen them.

Male webspinner (Embioptera) perched on hand.

A male webspinner with wings partly folded perches on a hand.

The Standard Bearer – Ensign Wasp

6 Sep
An ensign wasp (Evaniidae)

An ensign wasp (Evaniidae) perched on a wall.

Due to their long legs and antennae, an ensign wasp on a wall may resemble a spider from a distance, and like spiders, they ought to be welcome guests in a home.  These little wasps are unable to sting and harmless to humans, but they are deadly to roaches.  Like many other small wasps, ensign wasps are parasitoids:  the female ensign wasp lays her eggs only in the egg cases of cockroaches, where the larvae hatch and quickly devour the cockroach eggs.

Ensign wasps (also called hatchet wasps) are members of the family Evaniidae, and take their common name from the distinctive shape of their gaster (rear end).  It is flattened laterally, and attached high like a flag.  Much like a banner waver, they will twitch their gaster rapidly up and down when disturbed.  The species I find around here is also notable for the attractive blue eyes that can be seen under a hand lens.  They main body is perhaps 1cm long, with the legs and antennae nearly doubling the size.  I found the wasp pictured above hanging around in the hallways of our building on campus, defending us from roaches.

Techniques: Aspirator

3 Sep
Aspirating insects at a light sheet.

Aspirating insects at a light sheet (Welder Wildlife Refuge).

New page up in the techniques section.  Please check out my explanation of the aspiration technique for collecting small or delicate insects.

Find more techniques for insect collecting and rearing in the techniques section.