Nature News: Tracking a predatory stink bug

Anchor stink bug hauling this monarch caterpillar (already dead) around the milkweed plant Sue Pike Photo

Ever since my young cousins in New Jersey sent me photos of monarch butterfly eggs and tiny snow white monarch caterpillars with black heads (they don’t get colorful until later in development), I have been looking for the same on my milkweed plants. Unfortunately, the one and only monarch caterpillar I have found so far was dead, killed by a predatory stink bug. While great for the stink bug, this was, of course, tragic for the monarch caterpillar. We were unhappy as well since we have been encouraging milkweeds and planting all sorts of wildflowers in an attempt to create a safe haven for these beleaguered insects.

Initially, watching this menacing-looking bug drag the hapless carcass of the monarch caterpillar around, I was horrified and wanted to know who the culprit was. Identifying insects can be incredibly difficult. I tried some books and the internet, and I decided it was some sort of stink bug, perhaps an anchor stink bug. According to a “Featured Creatures” bulletin put out by the Florida Department of Agriculture and Consumer Services, the stinkbug “genus is recognized easily by the enlarged long and broadly oval scutellum (located behind the pronotum) … subapical spine on the front femora; and ventral pubescent patches on the males.” I didn’t know what any of that meant, so I resorted to iNaturalist and the awesome folks at bugguide.net for the final identification. My tiny predator did turn out to be an anchor stink bug (Stiretrus anchorago).

The red arrow points to the ‘anchor’ on the stink bug’s back. Not real obvious here. Sue Pike photo

Now that I knew what an anchor bug looked like, I decided to at least learn what one of those seemingly obscure anatomical terms referred to. I call myself a naturalist and, upon finding out what a scutellum was, realized I’m a fairly ill-informed naturalist. All true bugs have a hard plate, called the scutellum, that is usually triangular, on their backs. The anchor bug’s scutellum is unusually large and U-shaped, something like a shield with a black anchor-like pattern on it. Now that I knew what to look for, the scutellum was, indeed, a very prominent and recognizable feature.

While refreshing my memory on insect anatomy, I was reminded of some of the differences between insects that are known as true bugs (some common examples are cicadas, water striders, stinkbugs and spittlebugs) and other insects, like beetles (not true bugs). It can be difficult to identify insects down to their species, but once you know what to look for, you should be able to distinguish a beetle from a true bug fairly easily. Beetles have chewing mouthparts whereas true bugs eat a liquid diet. True bugs have a beak, which they use to suck out the contents of whatever it is they are eating. The anchor bug uses its beak to harpoon its prey and then inject digestive enzymes that first immobilizes the prey and subsequently turn its insides into goo, which they then suck up with those same beaks. If you look carefully at the photo, you can see a tubular structure attaching the anchor bug to the caterpillar — that’s the beak, firmly implanted in the caterpillar. A number of pests (aphids, for example) are true bugs that use their beaks to feed on the fluids inside plants.

The easiest way to know whether you are seeing a true bug or a beetle is the wings on the back. Beetles have hard, leathery forewings that cover up and protect the hind wings. When at rest, the hard forewings meet in the middle of the back forming a line down the middle separating the two wings. These have to be lifted out of the way when the beetle flies. Only the first part of the forewing of a true bug is hardened (hence the scientific name, Hemiptera, which means half wing). At rest, the wings cross over each other so that from above they have a triangular shape. All true bugs also have a scutellum in between the wings, sometimes it is reduced in size and sometimes it is big and obvious, like in the anchor bug.

Anchor bugs live solitary existences, roaming the landscape in search of prey and are considered to be economically beneficial insects. As generalist predators, they are good biological controls of a variety of pest species (though they really aren’t common enough to make a big dent in a pest population). Look for them in your garden or a nearby field, they are strikingly beautiful bugs with their bold patterns of black and red, yellow or white. Now that I know who they are, next time I see one, I will welcome it gladly and not judge it for killing the occasional monarch butterfly, being, as they are, important members of our local backyard ecosystems.

Nature News: Baltimore orioles are here for our bugs

published May 25th in seacoastonline.com and the Portsmouth Herald, York Weekly, Foster’s Daily etc

Male baltimore oriole Steve Morello photo/stevemorello.com

Our woods are starting to get extremely buggy, so much so I was thinking about ways to kill off mosquito and black fly larvae. I mentioned this to my son and was, luckily, brought back to my senses by his reply–”what about the birds?”.  We do have extremely buggy springs and summers, this is the reason many birds (neotropical migratory birds) migrate up from the tropics to breed in our forests.  They escape the competitive pressures of the tropics (so many species competing for the same resources) and instead spend the energetic capital to come up here where there are fewer competitors and tons of insects and fruit.  They don’t overwinter because the supply of food (insects and fruit) diminishes to unsustainable levels in the fall and winter.  So, I decided not to buy some mosquito dunks to toss into my ponds and let nature take its course.

Female oriole Steve Morello photo
stevemorello.com

One of the flashiest neotropical migrants nesting in our backyard this year is a pair of orioles.  I love these birds-they have a beautiful melodic song, weave intricate, pendulous nests and are so colorful.  The males are resplendent orange and black, while the females and juveniles are a lovely yellow with some orange patches on the breast, gray on the head and back, with two obvious white wing bars (the males only have one).  They are sturdy birds with long pointed bills-resembling the other members of their family-the blackbirds and meadowlarks. Knowing this relationship makes it easier for me to identify their call–it has that burbling quality of a meadowlark’s call.  We put out oranges at the feeder, along with some grape jelly, and they visit, scooping up brilliant globs of jelly that glow in the sunlight. 

This dates me a bit, but I always have to consult my most recent bird book about their name.  I remember when this species was combined with the Bullock’s oriole into one species called the northern oriole because there was so much hybridization where their ranges overlapped in the Great Plains.  Then, back in the 1990s (seems like yesterday), genetic studies determined that they are, in fact, two separate species and so they were given their old names back. 

My favorite thing about orioles, and perhaps the thing they are most famous for, is their nest-a dangling sock-like structure.  I’ve been looking around for the nest but haven’t found it yet–I thought they always dangled from a branch but this isn’t  true, sometimes the nest is anchored to the trunk of a tree.   The females are the weavers, constructing their nests in three stages.  First, the outer dangling sock, which she begins by looping long flexible fibers (grasses, bark, wool, old string or fishing line) over a tree branch and then pushing her bill through the fibers which tangles them and creates knots.  While random in nature these knots form a decidedly strong woven nest.  She’ll do one side first and often works from inside the bowl to shape the rest of the nest. She then adds springy fibers to give more support to the inner bowl and finally soft materials and feathers to line the bowl. (Cornell Laboratory of Ornithology).  It generally takes about one week to construct the nest.

While Baltimore orioles are certainly attracted to fruit and sugary liquids (like jelly or the hummingbird feeder) while raising young the majority of their diet are insects which provide the protein needed for growth.  In the fall and spring, before and during migration, their diet shifts to mostly ripe fruit and nectar-these provide the high energy sugars needed for the rigors of migration. 

If you want Baltimore orioles and other neotropical migrants (warblers, tanagers, etc)  in your backyard, don’t use pesticides.  Insecticides kill insects-essential prey for our migratory birds. Remember, the reason migratory birds come here isn’t to visit us, it is for our bugs.