Insect Ingestion

A Gulf Fritillary siphons nectar from a flower.

While taking insect photos over these last few months, I've become particularly enamored with photographing them while eating. It started with flies. (Doesn't it always?) I was watching a housefly using its spongy appendage to mop up traces of food on a plate when it occurred to me that my macro lens is powerful enough that I could photograph said appendage and it all went downhill from there. I found myself particularly taken with lapping and sucking flies. These flies have soft pads, called labellum, on the end of their proboscis that they use to sop up liquids.

(Disclaimer: I have done my best to accurately and simply describe the form and function of various mouthparts, but I am no expert and this post may contain inaccurate information. Also, you can enlarge any of these photos by clicking on them and totally should.)

The mouthparts of a lapping and sucking fly.

A fly with its proboscis extending...

...and retracting.

This hoverfly stretches its proboscis to great lengths to sop up pollen and nectar from a flower.

Another hoverfly uses its labellum to wipe traces of food off of a leaf.

Two primary types of mouthparts can be found among the members of the order Diptera (that's plain old "flies" to you and me): those wielded by the lapping and sucking flies and those wielded by biting flies. Biting flies do not bite, per se: they might better be described as "piercing" flies, as they conceal sharp, pointed mouthparts within their probosces that they use to stab their victims before drinking up the blood from the wound. Mosquitoes are the biting flies that we are perhaps most familiar with, but though I was bitten by mosquitoes while questing for insect photos, I did not capture any images of those famous bloodsuckers at work. My access to horses, however, provided me with an opportunity to photograph stable flies and during the month of July, it was virtually impossible for me to go out into my backyard without coming upon a robber fly sucking on a meal.

A biting fly's piercing equipment is hidden within its proboscis.

A stable fly springs into the air, ready to seek out blood from a nearby horse.

This stable fly pierces the skin on a horse's leg to get a meal.

The same protruding proboscis found on stable flies...

....can also be seen on robber flies both large...

....and small.

Instead of mammals, robber flies feed on other insects.

Flies are not by any means alone in the insect world when it comes to feeding by piercing and sucking. So-called "true bugs" and their closest kin--aphids, leafhoppers, and cicadas--also feed by stabbing their food and drinking up the fluids within, though, with exception of assassin bugs, almost all the insects in this category are vegetarian. (It remains one of my dearest wishes to photograph an assassin bug in the midst of a meal!) Aphids and their ilk have short "beaks," while true bugs are distinguished by the elongated labium (the bug's lower lip, in essence) extending from the proboscis and sheathing the piercing equipment. When not feeding, the labium, which is jointed, is folded under the body.

A true bug's piercing and sucking mouthparts.

A solo aphid uses its short "beak" to suck juice from a flower petal.

Tiny black bean aphids coat a plant stem. Sometimes their rear legs rise into the air as they feed, but their sharp little mouthparts remain firmly rooted in the stem!

This side view offers a good look at the jointed labium of a tarnished plant bug nymph feeding on a sunflower.

This adult tarnished plant bug's partially unfurled labium can be seen below its proboscis.

Butterflies and moths have the simplest (and probably most familiar, at least to anyone whose elementary school class studied butterflies) equipment for getting a meal: a long, thin, flexible proboscis that is carried coiled under the head. While flies and true bugs may send digestive juices down through their probosces to liquify their food before sucking it up, moths and butterflies are sippers pure and simple, using their flexible straws to drink nectar from flowers and occasionally minerals from a variety of sources.

Moths and butterflies have what are called "siphoning" mouthparts.

Whether you're a cabbage white...

...a swallowtail...

...or a skipper, you're drinking your meals through a flexible straw!

Things start getting a bit more complicated around the mouth when we look at bees. While lapping flies may use their labellum to clean pollen from their feet after a shuffling about on the face of a flower, the mouths of the insects we've looked at so far have been devoted solely to the acquisition of food. Bees, on the other hand, while obtaining nectar via a tongue sheathed by a tube-shaped labium, also need some equipment for duties around the hive, like molding wax. Thus, in addition to the mouthparts designed for lapping up nectar, bees are equipped with small mandibles, or jaws. Bees are considered to have "chewing and lapping" mouthparts.

A bee's lapping...

....and chewing mouthparts.

A honeybee's tongue is visible between her small mandibles as she pulls her head from a blossom.

A metallic green bee probes the depths of a cosmos flower for food. 

While a bee usually folds its proboscis under its head while not feeding, this bumblebee has left its tongue unfurled as it hurries between spikes of lavender.

The insect mouthparts covered above are, in fact, exceptions to the general rule of insect mouth anatomy, all of them adaptions of a model that centers around those laterally moving jaws called mandibles. Mandibles come in all sizes and are useful for many purposes besides the holding and cutting food.

This carpenter ant displays large mandibles that are strong enough to chew through wood.

A paper wasp (who, like a bee, feeds on nectar) uses her mandibles to collect and masticate plant fibers for nest material.

A flower longhorn beetle uses its mandibles to clean its antennae and limbs after a tumble into some cobwebs.

But back to eating...

These tiny ants are using their mandibles to remove crumbs from a piece of dog food.

An aphid disappears between a ladybug's mandibles.

A caterpillar's mandibles vanish entirely when it undergoes metamorphosis, but in the meantime, its powerful jaws can easily consume tough leaves. 

A honeybee and a tarnished plant bug feed
side-by-side on a sunflower.

I never seem to tire of watching bees efficiently hustle across a flower, probing each cranny for nectar as their legs grow fat with golden pollen, or hoverflies scrubbing every floret's anthers as they work their way across a lacecap hydrangea. I consider myself very lucky to have caught the image of a ladybug with an aphid in its jaws and am always on the lookout for the opportunity to do so again. In addition to wanting a photo of an assassin bug consuming a caterpillar, I'd love to get a picture of a dragonfly munching on something; the closest I've come is a not-very-good image of a damselfly with an aphid's leg hanging out of its moving mouth. For the time being, my best bet for photographing successful aerial hunters means keeping an eye on the robber flies, who, alas, have perished for the season. I'd also like to capture more insects eating leaves, but they all seem to prefer to do their munching after dark. Maybe next year will be the year!

A hoverfly swabbing a basil blossom.

Of course, sometimes you get REALLY lucky and capture a photo of something that you didn't even know existed. I was photographing a dragonfly nymph in a pond one day and was puzzled by the rapid scooping motions it was making near its mouth. To my eyes, it looked rather like it was using little arms, but that didn't seem possible, since all six legs were clearly visible. So I switched my camera to its action setting and took a bunch of photos, hoping that when I pulled the images up on my computer screen, I'd get a better idea of what was happening.

Dragonfly nymph.

Wow. What I saw on the screen was so cool that I gave a shout and a fist pump! The photos revealed the nymph's modified labium--or lower lip--acting as a membranous scoop that rapidly nets and delivers prey to the hungry nymph's jaws. I rank it as one of the coolest discoveries I've made with the benefit of my macro lens! 

Scoop!

This discovery also solved a mystery: the day before I photographed the nymph feeding, I took some photos of the nymph in the picture below sprawled belly-up on the surface of the pond. I couldn't tell what on earth that blobby thing on its face was. Once I saw the images of the nymph's eating mechanism in action, I realized that that slack membrane hanging from the dying nymph's face was the underside of the modified lip. As you can see, it's quite large! Dragonfly nymphs are known for being both voracious pond predators and speedy eaters, so it's really cool to have captured one in action!

Dragonfly nymph underbelly and lower "lip."

Insect photography, for me, is all about discovering new things about the world that surrounds me. An interest in insects naturally spawned this interest in insect behavior and I now have a much better understanding of not just who eats what and how, but of the underlying anatomy. In other words, I've learned something. What could be cooler than that? I hope from looking at my photos, you've learned something, too!

Here's a close-up of that crazy lip. Pretty cool, right?

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