Immature planthoppers hanging out in a fungal growth under a log.
I found these brightly colored insects tucked under a log in Arizona, where they appeared to be feeding on a growth of fluffy white material–perhaps fungi or mold. These are immature planthoppers, members of the same group of tiny hopping green specks you sometimes run into in lawns or trees. This was, for me, a pretty surprising place to encounter a hopper, so I looked around to see what else I could find out about these little fellows.
The lovely community over at BugGuide has tentatively identified these as members of the family Derbidae, based at least partially on the context I discovered them in. While adult derbid hoppers, like most planthoppers, are sap suckers, the nymphs of some species feed on fungi, particularly in rotten logs.
Because these hoppers are immatures, their wings have not yet developed (you can see the developing wing buds on their backs). Adult derbids typically have long, delicate wings for hoppers. In fact, they are noted for gathering to perch under broad leaves, a behavior which may protect their fragile wings (U Del).
Katydid nymph on a leaf (Tettigoniidae).
I found this impressively large katydid nymph hanging out at a gas station. I thought he provided a particularly clear illustration on the difference between adult and juvenile wings in grasshoppers, katydids, etc. Adult and juvenile orthopterans can generally be distinguished by the presence or absence of wings. However, like other hemimetabolous insects, juvenile grasshoppers and co. gradually develop their wings as they move through larval molts, so later instars have signs of small, developing wings (wing pads or wing buds). Moreover, some orthopteran species are brachypterous (short-winged) or apterous (wingless) as adults, further complicating the matter. In collections, which generallly exclude immature insects, such species are notoriously underrepresented.
So the question is, how does one distinguish final instar grasshopper and katydid nymphs (those in the last juvenile stage prior to adulthood) from short-winged adults? Here’s the trick as I learned it from my labmate Paul Lenhart.
Final instar katydid nymph grooming its hind leg.
It took me a while to develop an eye for this, but the principle is fairly straight forward. In the last nymphal instar before adulthood, orthopteran wings “flip.” The hind wing (eventually to become the large, fan-folded flight structure) sits on top of the forewing (the elongate leathery tegmina which will protect the hindwing in adulthood). You can see this in the picture above. The main, costal vein of the hindwing is located dorsally (at the top), with a fan of veins running downwards, giving the characteristic “D” wing shape of a nymph.
Sexually dimorphic male and female grasshoppers mate.
After the molt to adulthood the wings flip again, tucking the hindwing under the forewing with the costal vein now located ventrally (to the bottom). Compare wings of the katydid nymph above to the more elongate, “U” shape of the forewing seen in these adult male and female lubber grasshoppers. The veins in the short forewing of the brachypterous female run mostly parellel, rather than fanning downwards.
The extended spoon-shaped labium of a libellulid dragonfly nymph.
One of my favorite examples of weird insect anatomy are the strange mouthparts of the aquatic nymphs of dragonflies and damselflies. A close look at the faces of these creatures reveals large hinged structure folded back under the head. In the case of the nymphs of Libellulidae, this structure actually curves up and wraps around the face, very much like a Darth Vader style mask. What are these structures?
Ventral side of libellulid dragonfly nymph, showing the spoon-shaped labial mask.
All Odonata larvae have a prehensile labium, sometimes called a labial mask, which folds under the head and thorax. This lower lip is capable of extending rapidly forward, striking prey before they can react. Hooks on the ends snag the prey and draw it back to the mandibles. All in all, the feature is reminiscent of a frog tongue snatching flies.
Ventral side of aeshnid dragonfly nymph, showing the flat, blunt labial mask.
An aeshnid dragonfly nymph preys on a libellulid dragonfly nymph.
Last week I posted pictures of some dragonfly nymphs, and Jim Johnson of Northwest Dragonflier was kind enough to give me some ID tips in the comments as well as pointing out I had two different types of dragonfly larvae. Taking another look at the nymphs, the differences were not only really obvious but really interesting. So I took a bunch more pictures and made two more posts.
The two larval types I was observing belong to the dragonfly families Libellulidae (skimmers) and Aeshnidae (darners). As can be seen below, libellulid larvae have short, stout bodies with widespread legs that lend them a toad-like appearance. Aeshnid larvae have elongate, torpedo-like bodies and move about much more actively. These two body types are indicators of the two families’ very different lifestyles under the water.
Early instars of libellulid and aeshnid dragonfly nymphs (sprawlers and climbers).
Libellulid larvae are “sprawlers.” These larvae are fairly inactive, instead lurking under mud and debris at the bottom, ready to snatch potential prey that get too close. Special hairs on their body trap debris, further camouflaging them and giving them a fuzzy, almost moldy appearance. In contrast, aeshnid larvae are sleek and aggressive little predators. These “climber” larvae move rapidly through the water, actually jet-propelling their streamlined bodies by taking water in through their mouth and expelling it out their anus. Within half an hour of my moving a few nymphs into a smaller container to observe, the aeshnid pictured here had made a meal of both his libellulid tank-mates. Climber type larvae are more visually dependent than sprawlers, and their eyes tend to be larger and more developed. They also climb vegetation, moving into different water levels rather than resting on the bottom.
A few more categories exist–“clingers,” with adaptations to allow them to remain stationary in flowing water; and “burrowers,” which, as the name suggests, burrow into the mud or dirt. Aquatic insect larvae that can move freely about through the water are called “swimmers.”
An aeshnid dragonfly nymph shown on thumb for scale.
Final instar nymph of an aeshnid dragonfly (College Station, TX).
Two years running our first planned field outing for the spring has coincided with one of Texas’s rare dips into below freezing weather. While fishing around in lakes is not the ideal pasttime for this kind of temperature, it is a decent way to get hold of some insects even in cold weather. One group of insects that’s a relatively common find are the aquatic immatures of dragonflies and damselflies. The dragonfly nymphs in particular are striking little creatures, with the earlier instars resembling squat little brown frogs. Like their adult incarnation, they’re also impressive predators, even tackling small fish.
Early and late instar dragonfly nymphs (Libellulidae, Aeshnidae).
Dragonflies lack a pupal stage, so the developing wings (wing pads or wing buds) can be seen in the late immature instars. I hadn’t caught a final instar dragonfly nymph before, so I was suitably excited to see one up close. The larger fellow above even obliged us by molting into a pretty blue darner during the middle of a lecture on dragonfly metamorphosis to a group of introductory entomology students.
*edit* Thanks to Jim Johnson for family corrections and additional information about nymphal characters.
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.
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 spittlebugs.
Katydid nymph on a leaf.
Katydids are a member of the order Orthoptera (grasshoppers, katydids, crickets, etc.) and the family Tettigoniidae. Orthopteran nymphs, or immatures can be distinguished from adults by the development of their wings. Only adult insects have completely developed wings (think butterflies, beetles, and flies). Immature insects have not yet developed wings (think caterpillars, grubs, and maggots). Katydids, like other orthopterans, have incomplete metamorphosis, meaning they lack a pupal stage (think chrysalis or cocoons). Instead, the immatures generally resemble the adults in appearance, and partially developed stubby wings, called wing pads, may be present in some of the later molts. The nymph above is very young, and has no wings or wing pads present.
Here’s a picture from my own backyard in Texas!
A tiny katydid perches on a leaf.
Katydids are also called ‘long-horned grasshoppers’ in reference to their long antennae. Orthopterans of the suborder Ensifera, or ‘sword-bearing’, generally have antennae longer than their body length as well as exserted ovipositors (sword-like egg-laying tubes that allow females to saw their eggs into plants or insert them down into the fround.) Thus, katydids (like crickets) can be distinguished from grasshoppers by their long slender antennae and legs.
Below, you can see a grasshopper nymph, from the suborder Caelifera. This grasshopper is a member of the family Acrididae, the ‘short-horned grasshoppers.’
A grasshopper nymph perched on a fingertip.