Just a random picture of a crab spider with a mirid lunch all wrapped up. Plant bugs seem to be a popular lunch item in my neck of the woods. Of course, they’re the largest true bug (Hemiptera: Heteroptera) family, mostly herbivores, and conveniently snack-sized.
One interestingly little bug family that I have occasionally stumbled across while peeling back bark is the flat bugs, family Aradidae. As their name suggests, these bugs are notable for their extremely flattened body morphology, an adaptation to their lifestyle under bark and in crevices of wood. These guys are hard to spot, being cryptic both in body and lifestyle, but, as an example of morphology pushed to the limits, they are impressive to observe.
Because these bugs are of little economic importance (they are rarely agricultural pests) little research has been done on them. Nonetheless this is a diverse group which is found worldwide. Most flat bugs feed on fungi in decaying wood, and some are attracted to the pheromones of bark beetles, which may help them to locate food sources. These bugs tend to be found in gregarious groupings. Probably the best gathering of information that I have found on aradids is Steve Taylor’s info page, complete with some great pictures.
So one random factoid I encountered while researching milkweed bugs last week is that you can distinguish males and females by the markings on the underside of their abdomens. Females have a black stripe and two black dots, while males (the smaller sex) have two black stripes. I didn’t have a male to draw comparisons against last week, so I tracked down a neighboring lab colony of milkweed bugs and sure enough, boys and girls! (Thus resolving any future crises I may have involving the gender identification of milkweed bugs.)
I had originally wanted to photograph a mating pair, but apparently they found being repeatedly flipped onto their backs disruptive. I finally resorted to sticking them in the freezer for a few minutes, after which they gave a very good impression of being dead (slightly too good an impression). Luckily they eventually perked back up and I got a few photos.
I love Texas–when I’m not complaining about the heat–because you can find insects virtually year round. In December I was playing with earwigs and now it’s January and already the fire ant mounds are popping up everywhere like spring flowers. (Working with fire ants has severely warped my perceptions of this event.) I found this large milkweed bug (Oncopeltus fasciatus) sunning itself today in the balmy 70 degree weather. Bugguide.com lists these fellows as active only from May to October, at least in North Carolina, which is apparently because North Carolinians have an odd phenomenon known as ‘seasons.’
Milkweed bugs belong to the true bug family Lygaeidae, the seed bugs. Like other members of the family, milkweed bugs make their living feeding on nutrient rich plant seeds, in this case usually the seeds of the eponymous milkweed plant. (Yes, this entire previous sentence was an excuse for me to use the word ‘eponymous’.) They use their tubular mouthparts to pierce the walls of seed pods, feeding on the seeds within.
Like that other famous milkweed feeder, the monarch butterfly, the bright, warning coloration of milkweed bugs warns predators that these bugs sequester toxic compounds from the plant in their bodies, making them distasteful. Milkweed bugs can be fed a variety of other seeds, although interestingly they habituate to food types and it often takes several generations for them to make a switch. Milkweed bugs in the lab are generally fed sunflower seeds, shelled or cracked since their mouthparts can’t pierce the harder husks.
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.
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.
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.
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.
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.
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.
Exploring an Argentinean roadside I spotted what I thought was a dead wasp on a flower. Wondering how this wasp had come to perish so abruptly in her nectar gathering work, I looked closer. I actually poked at her several times before I noticed the second occupant of the flower—an ambush bug enjoying a tasty wasp meal!
Ambush bugs are a subfamily of Assassin bugs, family Reduviidae. Ambush bugs are “sit-and-wait” predators. These highly cryptic (camouflaged) insects frequently lurk around flowers, where they pick off unwary visitors. They have mantis-like raptorial forelegs to snatch their prey from a safe distance. Like other true bugs (order Hemiptera, suborder Heteroptera) ambush bugs have a segmented tube-like ‘beak’ for feeding. Ambush bugs insert this beak into a weak spot in their prey’s hard exoskeleton and suck out the fluids.