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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.

Ants and Hoppers

6 Aug
Carpenter ants (Camponotus) tending treehopper nymphs (Membracidae).

Carpenter ants tending hopper nymphs in Argentina.

Since we had the spittlebug nymphs earlier this week, I thought I’d take the opportunity to post a picture of some other hopper nymphs.  These little guys are being watched over by several carpenter ant workers, who will collect their sugary excretions and protect them from predators.

A casual observer might confuse these with mealybugs due to their white, somewhat waxy appearance and their location feeding en masse on a plant stem.  (This casual observer would in no way be me.  Nope.)  However mealybugs, like scales, have reduced appendages and secondarily lost wings.  A close look at these guys will reveal not only well developed legs peeking out, but the presence of small, developing wing buds on their backs, indicating that they are late stage nymphs (immature insects).  In fact, that dark shape near the middle left of the mass appears to be an adult thorn-mimicking treehopper, making it likely that these are members of the auchenorrhynchan family Membracidae.


2 Aug

Spittlebugs (Cercopidae) on a plant stem.

Spittlebug nymphs on a plant stem.

Spittlebugs lay their eggs on plant stems.  The young spittlebugs excrete special fluids which they whip into a foamy mass around themselves (in the above image some of this foam has been wiped away).  This ‘spittle’ serves to protect the nymphs from predators as they develop, feeding on plant fluids.  They grow and molt several times (one of the cast off skins can be observed in the above picture), finally leaving the spittle mass after the last molting into their adult form.  Some predatory insects lurk by spittle masses, patiently awaiting the emergence of the insects.  Spittlebugs may live alone or in groups, and the nymphs sometimes leave their own spittle masses to find a new spot or join other spittle masses.

Spittlebugs (family Cercopidae) are in the hemipteran suborder Auchenorrhyncha, and thus are related to leafhoppers, treehoppers, and even cicadas.  The adult insects resemble broad and stout-bodied leafhoppers, and are sometimes called froghoppers due to their somewhat frog-like appearance.

Close up of spittle bugs.

Close up of spittlebugs.

At the Aphid Bar

23 Jul
Sugar ant (Brachymyrmex) tending aphids on flower bud.

Sugar ant (Brachymyrmex) tending aphids on flower bud.

As mentioned in a previous post, many phloem-feeding hemipterans, such as aphids, take in excess sugar, which they excrete as a substance called honeydew.  This sugary substance attracts other sugar feeding insects, which has led to some interesting interactions.  Among the most notable is the development of a mutualistic, or symbiotic, relationship between some ants and aphids.  Ants may ‘tend’ aphids, drinking the honeydew and protecting the aphids from predators in return.  This provides the additional benefit to the aphid of preventing the build up of their sugary excrement which could encourage the growth of fungi and mold.

Carpenter ants (camponotus) tending aphids.

Carpenter ants (Camponotus) tending aphids. A parasitic wasp perches on the edge of the leaf.

Ant-hemipteran interactions can be observed almost anywhere if one takes the time to observe closely.  I found the carpenter ants above tending aphids on the bushes right outside my front door.

Of course, as in any biological relationship, cheaters exist.  Some ants tend aphids without providing any protection against predators.  Some aphids manufacture less nutritious honeydew.  On the other hand, some ants take their care of aphids to extremes, even building structures to protect the aphids against winter cold.

Silhouette of carpenter ant tending aphids.

Silhouette of carpenter ant tending aphids.

Sunny Suckers

19 Jul
Aphids on a flower.

Aphids nestle under the base of a flower in Sam Houston National Forest.

Anyone who has spent much time around plants will be familiar with this classic gardener’s pest, the aphid.  Aphids use their piercing-sucking mouthparts (a characteristic of the order Hemiptera)  to drink the fluids of plants.  Fluid uptake occurs passively via the pressure generated by the plant’s own circulatory system.  In fact, the aphid’s mouthparts actually contain valves to limit the flow.  Without such systems the aphid would literally be blown off the plant.  It is more the equivalent of attempting to drink from a firehose than sucking from a straw.

Aphids are gregarious insects which live in small subsocial colonies on plants.  Reproduction varies among aphid species and may be sexual or asexual.  Many aphid species give live birth to young.  In the picture above and below, a few white and shriveled cast off exoskeletons are visible from developing aphids.  These skins, called exuvia, can become quite numerous as colonies grow and become crowded.  Overcrowding on plants generally triggers the production of winged aphids, which disperse to new host plants where they found new colonies.

Aphids coat a plant stem.

Aphids coat a plant stem in Argentina.

Minute Monster – the immature ladybug

9 Jul
Baby ladybugs!

Baby lady beetles munching aphids.

Another picture from right in my backyard!  Unlike their pretty and popular adult form, ladybug larvae look a bit like they ought to be featuring as monsters in a horror movie, and they are indeed fearsome predators.  (At least of the very tiny.)  But just like grown up ladybugs these strange critters are the gardener’s friend, since their favorite prey are aphids.  Another trait they have in common with adult lady beetles is their bright coloration.  This aposematic, or warning, coloration serves to alert predators that they are not good to eat, due to the toxic chemicals they sequester in their bodies.

Lady beetles belong to the family Coccinellidae, which takes it name from the word coccus, meaning circular, due to the adult beetle’s nearly circular shape.  They are also generally almost flat on the bottom, allowing them to draw their legs under their armored exoskeleton and fit almost perfectly against a plant surface when under attack.

Le Pew – the Stink Bug

5 Jul
Stink bug on tree

A stink bug climbs a tree.

These large, cryptic stink bugs have been hanging around the trees by my house lately, often clustered up against the bark and nearly undetectable by casual observation.  Like other hemipterans, stink bugs (or pentatomids) have sucking mouthparts, which they use to feed on plant matter.  We also have a fairly common bright green stink bug that does a good job blending in with leaves and stems.

Stink bugs get their common name from the strong deterrent odor they emit when disturbed.  This smell, combined with an unpleasant taste, helps to ward of predators.  This is not unique to stink bugs, however:  several other hemipteran families also have scent glands.  Unlike such smelly animals as the skunk, I find the smell of stink bugs not particularly unpleasant–a bit like sickly sweet fruit.  A casual survey of various people I have had the opportunity to quiz on the subject (“Here: smell this bug!”)  supports my opinion.

The stink bug family name Pentatomidae means “five divisions”  which may refer to the five-segmented antennae (many other hemipterans have only four) or the somewhat pentagonal body shape.

Stink bugs clustered on bark

Cryptic stink bugs on bark.

Damsel and Prey – the Narrow-Winged Damselfly

14 May
A damselfly with captured leafhopper.

A damselfly with captured leafhopper.

Found this damselfly in Argentina, munching on a tiny leafhopper.

Damselflies (Odonata, suborder Zygoptera:  “paired wings”) can be distinguished from dragonflies by the shape of their hind wings, which are similar to their forewings, narrowing at the base like a petal.  Dragonflies (Odonata, suborder Anisoptera: “unequal wings”) have a hind wing with a broad, lobed base.  Additionally, as their names would suggest, dragonflies tend to be larger, and thick-bodied, while damselflies and small and slender.

Both dragonflies and damselflies are agile predators, snatching flying prey out of the air.  Damselflies have a special adaptation for this.  They use their forward angled legs to form a ‘basket’.  Long bristles on the legs complete this structure, allowing the damselfly to sieve prey from the air.  Once caught in the ‘basket,’ the prey is then transferred to the jaws of the damselfly.  In this case, the damselfly has caught a leafhopper, family Cicadellidae.  A close look will reveal that this family tends to resemble tiny hopping cicadas, a relative in the hemipteran suborder Auchenorrhyncha.

Ants and Scales

26 Mar
Carpenter ants tend scales on a shrub

Carpenter ant workers (genus Camponotus) tend scales on a shrub in Argentina.

Scales (superfamily Coccoidea) are members of the same suborder of hemipterans as aphids, mealybugs, and whiteflies (Sternorrhyncha) but are just a little more bizarre.  They are the barnacles of the insect world.  These strange little insects have adapted to a point where they no longer need to move to gather food.  Their tube-like beaks are plugged into the plant equivalent of blood vessels, which carry nutrients to them.  Adult female scales thus no longer need trouble themselves with developing such trivial things as legs, antennae, eyes and wings, and are almost unrecognizable as insects.  The males, on the other hand, resemble small flies, and flit among plants in search of buxom, blob-like females to mate with.

While feeding on the phloem (or sap) of plants, scales take in an excess of sugar compared to other important nutrients such as protein.  To counter this, scales (and many other hemipterans) excrete a sugar rich liquid called ‘honeydew.’  Honeydew often attracts other insects such as ants, who drink the honeydew and sometimes tend the scales like milk cows, protecting them from predators.

A carpenter ant (Camponotus) tends scales on a grass blade.

A carpenter ant (Camponotus) tends scales on a grass blade.