Sunday, September 17, 2017

Walnut Sphinx Moth

Walnut Sphinx Moth - REK
Over the last several weeks I have photographed many different moths coming to our Bull Creek deck light.  My favorite wasn't one of the showy giant silk moths but this more humble walnut sphinx moth, Amorpha juglandis.  The picture above is its usual resting position that I had been seeing several every night.

The female moth emerges from its cocoon and spreads its wings to dry.  It also spreads its pheromone over the air to attract a male.  Once fertilized she will fly off to lay 200-300 eggs on an appropriate food plant.  Her caterpillars will eat the leaves of a variety of trees including butternut, hazelnut, hickory, hop-hornbeam, and of course, walnuts. Like the giant silk moths, they have no intestine and live less than a week.

 Walnut sphinx caterpillar with its horn -  MJ Hatfield CC
Like other moths, the caterpillars serve as a food source for lots of spiders, birds and insects.  A dramatic example is the walnut sphinx caterpillar parasitized below.  Chris Barnhart found it on a dried up leaf and we identified it by the color and its distinctive "horn" at the end of its abdomen.

Parasitoid cocoons on a dead walnut sphinx moth caterpillar - REK
The most likely parasitoid is a Braconidae. The female lays eggs on the caterpillar and the young burrow into the caterpillar which continues on with life, chewing leaves happily while the young grow in its body.  Eventually they make cocoons and the caterpillar's health fails.  They are careful to avoid killing the caterpillar until they are full grown and ready to emerge.
"Most life histories involve parasitizing hosts as diverse as aphids, bark beetles, and foliage-feeding caterpillars. Many species are egg-larval parasitoids, laying eggs within host eggs and then not developing until the host is in the larval stage. Unlike ichneumon wasps, many pupate in silken cocoons outside the body of the host and others spin cocoons entirely apart from the host.(3) Also unlike ichneumonid wasps, very few braconids use host pupae to complete their life cycles, except for fly parasitoids in Alysiinae and Opiinae." from Bugguide
Empty cocoons - click to enlarge
Unfortunately we found this one when they had all left their cocoons.  I kept it in a sealed box in case there was one left but had no luck, just like the poor caterpillar.

The sphinx moth itself is a cool creature which is able to whistle at a high pitch, out of our hearing range but heard by birds. We wrote a blog about this some years back.  The sound comes out of the most distal spiracle and I wonder if that may be why it holds its rear end up.  On the other hand, it may just be showing off.

Monday, September 11, 2017

One Cool Toad

My third grade colleague, Bruno, is a great hunting companion.  Curious, quick and built low to the ground, he is now feared by every amphibian and lizard along Bull Creek.  He caught three small toads over an hour within fifty feet of our house, not to mention a number of 3" skinks.  The little toad above was different from any I had seen before so I sent it off to Brian Edmonds who responded rapidly that it is a dwarf American toad.
"Dwarf American toads are confined more or less to the Ozarks. They are smaller than other American toads and are often reddish in coloration. The red spots are diagnostic."
Our "garden variety" toad along Bull Creek is the American toad, Anaxyrus americanus.  It turns out there are three subspecies.  The eastern American toad, Anaxyrus americanus americanus, is the one we all know and love, warts and all.
"The eastern American toad is medium-sized and has a large, kidney-shaped gland called the parotoid gland behind each eye. The pupil of each eye is horizontal. This toad may be gray, greenish gray, or various shades of brown. The dark spots on the back may encircle 1–3 warts. The belly is white with dark gray mottling. The call is a sustained, high-pitched musical trill lasting 6–30 seconds."  MDC Field Guide
"A little privacy please."  The male is considerably smaller than the female.
Toad eggs - REK
Mating begins with the long trills of the male's love song.  Breeding occurs in small ephemeral ponds or collections of water.  The photograph above was taken at a puddle left by a flood in 2011.  The female will lay 2,000 to 20,000 eggs in long double strands which develop into tadpoles over 2 months.  This is a risky business as the pond can go dry and eggs are high on the diet of many things living around the pond.

The tadpoles, like the adult, secrete a protective chemical from their skin called bufotoxin which can make predators sick.  It can be irritating to our mucous membranes and can make your dog sick but as mentions "toads have little defense against boys" who can be very destructive in breeding season.

Back to Bruno's find, the dwarf American toad, Anaxyrus americanus charlesmithi.  "It is smaller (only about 2 inches, snout to vent) and more reddish brown, with fewer, smaller, or no dark spots on the back; belly is cream colored with a few dark gray spots on the breast. " (MDC)  The parotoid gland is much less prominent as seen above.

The proper grip - note the red dots
When holding a toad or frog for photography, pinch a front and back leg on one side between your thumb and fore finger and they will stop kicking and hold still, but they still won't smile for the camera.  I taught Bruno this trick but he couldn't teach me how to pounce on them.

Extensive information on both species is at this site.

Saturday, September 9, 2017

Red-backed Black Widow

Gala sent me this picture of a black spider resembling a black widow but with red on its back.  She wisely didn't pick it up to see if there was an hour glass on its tummy.  We had written about black widows in several blogs and all the widows I have seen had pure black backs so I doubted this was a black widow.  It turns out I was wrong, not a surprise to my wife, Barb.

This is is a northern black widow, Latrodectus variolus, a different species from our southern variety, Latrodectus mactans. Here is what Bugguide says about it:
"For the northern black widow, the hourglass is distinct, but is broken(1) (whereas the southern black widow's hourglass is complete) and typically there is a row of red spots down the middle of the back and possibly some diagonal whitish bands on each side; the bands are typically observed on the younger, more juvenile widows."

Two days old
Sealed in a magnifier box - lots of tape!
A few years ago we blogged about how male black widows danced to avoid being eaten. This included the egg sacs that we raised in our house at the creek. I say "we" as Barb put up with it with a lesser degree of enthusiasm. Having raised them, I felt a degree of a paternal relationship and was conflicted about what to do with them. They handled part of the problem as their numbers declined daily due to cannibalism of their siblings. In nature, if all the spiderlings are the same size, cannibalism is less common.*

Eventually I was out voted in releasing them and they stayed sealed up for a year to ensure they were neutralized. I felt better knowing that a female will have 9 to 15 eggs sacs with 100-900 eggs apiece over her lifetime so she probably didn't miss these.

* How black widow mothers control their children’s cannibalism

Thursday, September 7, 2017

Horse Fly Larvae

Horse Fly Larva
We recently wrote about the horse fly, the big buzzing pesky devils whose females bite to obtain blood necessary to produce their eggs.  I just came across one of their kids deep in a gravel bar.

I was with Deb Finn and Nathan Dorff of MSU, exploring gravel bars along Bull Creek as research sites.  We hiked up Peckout Hollow, an ephemeral drainage that has been dry for weeks.  There we found an uprooted tree and a deep hole washed out by a previous flood.  In the bottom there was a small shallow water pool a foot in diameter.  Nathan began digging away the gravel and came up with this horse fly larva.

"The larvae are long and cylindrical with small heads and twelve body segments. They have rings of tubercles (warty outgrowths) known as pseudopods round the segments, and also bands of short setae (bristles). The posterior tip of each larva has a breathing siphon and a bulbous area known as Graber's organ." Wikipedia on Horse Fly

Horse fly larvae generally are found in freshwater streams and moist soil.  Finding this one far from the creek is a reminder that water continues to flow under apparently dry gravel bars.  They even found a small crawdad!  Nathan's interest is in studying the ecology of water under the gravel and the invertebrates living there.

My favorite way to see a horse fly.
The larvae of most horse fly species are predators, feeding on worms and insect larvae although some of the larger species will attack tadpoles, frogs and toads. Unlike a lot of fly larvae, mine seen in this video manages to get around quite well with its six stubby legs.  They can have toxic saliva that helps to subdue their prey.  Depending on the species they can go through 6 to 13 molts before forming the pupa.  There is one generation per year but some species will develop to adulthood over 2 years.*

Having recently been tormented by some of its kin, I felt no guilt in keeping this specimen to the end of its life.  It may mean one less bite on my next hike up the hollow.
*Purdue University Entomology Extension

Wednesday, August 30, 2017

News Bee

Yellowjacket hover fly, Milesia virginiensis - REK
There are a lot of yellow flies on the flowers now.  These are Syrphidea family members, aka. hover fly, flower fly, or syrphid fly.  At first glance they are confused with yellowjacket wasps but there are significant differences in shape, size and flight pattern. 

Syrphid flies hover around flowers before landing to feed on nectar and pollen.  They look dangerous but they have no bite or sting and are entirely harmless.  Not so with their larvae which are predators on garden pests like aphids, scale insects and thrips.  They can destroy hundreds of aphids overnight, and when lady beetle populations are low they become the dominate predator.

My favorite is the yellowjacket hover fly, Milesia virginiensis, seen above. It is a noisy creature and its sound and pattern is distinctive enough that I don't usually even look to identify it. At first glance its hornet body shape and loud buzzing are threatening, a great example of Batesian mimicry to avoid predators, but watch it closely and it just wants to be friends.  It is a very friendly and curious insect that seems to enjoy human companionship.  It's known as the "news bee" for its habit of hovering relatively close to your face as though it was delivering the latest gossip.  No other insect does this and its behavior is as distinctive as its markings.  It is said that it's good luck if one can get the insect to perch on a finger.*  Given their sound and appearance, it is more a mark of bravery.

M. vrginiensis has a stalking behavior in mating.  The male hangs around flowers in the morning looking for females, then moves to areas where the females lay their eggs later in the day.  For those wanting to take a stab at insect identification, has this description that you can compare with the pictures.
"Traits of the adult to watch for include: a completely yellow face; yellow to light brown antennae; yellow femora and tibiae, with the tarsi somewhat darker. Wings cloudy but unpatterned, typically darker at the apical end."
Sphecomyia vittata female - REK
Many other flower flies mimic yellowjackets, possibly because of their aggressive traits and unpredictable gang warfare.  This one wasn't hovering as usual and when I compared the markings it was a close mimic of M. virginiensis.  It fits many of the features described above but the thorax and abdominal markings are far different.  This is why amateur entomology is fun!

Toxomerus marginatus male - ID by James Trager
This specimen was obviously quite different.  I was lazy that day and sent it off to Bi-State Bugs where James Trager IDd it as a male Toxomerus marginatus.  It took me a while to discover how he could identify it as a male.  It turns out that the eyes have it.  The males have bigger eyes - they have to find the females who are hanging out in a flower bar, just waiting to be picked up.  The guys have to be able to tell the difference in sexes to avoid wasted time and embarrassing encounters.
"Like all other flies the males have bigger eyes which come closer together at the top of the head. Females have much smaller eyes, placed farther apart. Tiny eyes or ocelli are composed of single cells and are found at the top of the head in a triangle between the large compound eyes."
Now with your new-found knowledge about sexing (not sexting) a hover fly, you can see that this specimen I photographed was a female.  You are now off on your way to being an entomologist!  Just a few more years to go, but a warning.....It can be addictive.
* Kaufman Field Guide to Insects of North America

Monday, August 28, 2017

Midwest Brown Snake

While standing around waiting where I park my truck, I randomly picked up a small slab of bark and found this snake.  My first guess was an eastern garter snake, Thamnophis sirttails sirtalis, but Brian Edmond corrected me.  This is a midland brown snake (MBS), Storeria dekayi.

The MBS is described as shy and secretive, living a quiet life in moist leaf litter, feeding on slugs, snails, and earthworms.  Its blunt head and backward pointing teeth are thought to be an advantage in eating snails.  They can hang onto the snail's head for a long period of time until it is fatigued and can be pulled out of its shell.

MBS has tan and brown skin with subtle spots that is perfect camouflage for its habitat. It has a slightly rough feel due to keeled scales along the back, longitudinal ridges like the keel on a canoe.  Unlike the garter snake which tries to act tough with false strikes and trying to bite, this docile snake just wanted to get away.

As I held it for pictures it would flicker its tongue.  I realized I could get its tongue out by holding my finger in front of it.  This video shows our snake's tongue in slow motion.  A snake's tongue can detect nonvolatile chemicals that its nose can't smell.  It is a way to identify prey as well as identify others of its species and chose a mate.*  It may also be involved it following the trail of prey although this is still being debated.

Brown snake smells with forked tongue - REK
Like other snakes, our friend has a forked tongue and I started wondering why that adaptation that is common to reptiles, most snakes, and a few lizards.  It turns out that it increases the surface area of the tongue to pick up smaller amounts of chemicals.  Also this gives the animal a sense of left-right direction from odors, similar to how ears on both sides of the head help us locate sound.

Our MBS was only twelve inches long and is unlikely to be mistaken for any venomous snake except a young pygmy rattlesnake.  Hopefully it will live a long and snail-full life, if it doesn't get under my truck.
* Of_tongues_and_noses
Thanks to Linda Bower for editing the video.

Friday, August 25, 2017

Horse Fly

We wrote about the bolete mushrooms on the glade in the last blog..  The day suddenly turned ugly as I was writing on the mushroom.  I heard a menacing buzz and felt a sharp pain on my back.    From then on for the next 20 minutes I had a dark Horse Fly  circling me and landing between my shoulder blades every minute biting me through my tee-shirt.  Swatting at it with my slouch hat had no effect as it followed me for a hundred yards.

Usually in encounter them on the creek and getting about 20 feet from their territory gets them off my case.  Not so this time as it followed me for several hundred yards through the woods, constantly buzzing and when silent it had landed and was biting through my sweat soaked tee-shirt.

Horse Fly - REK
I generally love nature in all forms.  We watch timber rattlesnakes by the garden and nudge them on their way.  We transfer spiders out of the sinks and haul rat snakes out of our attic at intervals.  When possible I capture insects, cool them in the refrigerator (thank you Barb for your tolerance) and photograph them alive before releasing them back to nature.  However I have to admit that I thoroughly enjoyed putting a pin through this bugger.

In the last blog I said we were "Blood Brothers" but not exactly, more like blood siblings.  Only the female bites, acquiring blood as a high-protein food needed for egg production.  I would happily take out a hard boiled egg or even a piece of last nights beef dinner for her but she is very specialized and wants only mammal blood.  Horse, deer or me, it makes little difference to her.

"The better to bite you with, my dear!" - REK
Adults wide ranging as this one was 150 feet above the creek bed.  The larvae live mostly in wet soil along the margins of streams and ponds.  While adult females feed on vertebrate blood, usually of warm-blooded animals, males and a few female species visit flowers.  Their larva are mainly carnivorous.  The female is well equipped to draw blood from the thick hide of a horse or the thinner skin of the primitive bipeds that came across the land bridge 13,000 years ago to provide an alternative blood source.
Wikipedia with annotations
"The bite is effected by stabbing with the mouth parts and slicing the skin with scissor-like movements of the finely serrate, knife-like mandibles and smaller maxillae. After capillaries are ruptured, anti-coagulant saliva is pumped out through the hypopharynx, and the blood is lapped up using the labella." from Bugguide
I have to admit that after my experience on the trail it gave me great pleasure to pin this Horse Fly for the upcoming Master Naturalist training where we will be using it for insect taxonomy.  It is not about revenge.....OK, maybe a little.
Horse Fly in Wikipedia
More on the Tabanidae Family,  commonly known as horse flies, and deer flies

Wednesday, August 23, 2017

Lurid Fungus

Hiking a trail above our glade I encountered these bolete mushrooms, tan to orange on top and slightly velvety on top.  When I bent it some, the stalk showed some blue-green streaking suggesting that it would show bruising.  With a small twig I wrote on the surface and sent it to Mark Bower.
"Your bolete is the “Lurid Bolete”, Boletus luridus. The tipoff is the orangish pore surface, the blue staining, the reddish reticulation on the stem, the reddish base of the stem, and the “root” at the stem base. Note that “lurid” doesn’t always have a naughty connotation!"
This is a common fungus which is found on both continents ranging across Europe and into China.  It is mycorrhizal, meaning that it grows on tree roots in a symbiotic relationship.  The fungus' mycelium extend far beyond the plant's roots to collect minerals in trade for nutrition from the tree.  This is far more common than we appreciate and is a field of intense research.

Click to enlarge - if you dare!

Lots of other common fungi like our beloved morels are mycorrhizal but some others are less glamorous.  Mark recently sent me the picture above of his latest find, Pisolithus tinctorius, aka. the Horse Dung Fungus.  If you think this is bad, you ought to see other versions at right as Mark photographed it.  This is not his usual artistic work.

An article in Scientific American had a lot of positive things to say about this fungus.  It has been found to partner with over 50 tree species.  Research on some mycorrhizal fungi has shown that the fungus can even exchange resources between trees of different species.  Michael Kuo in explains it this way:
"Pisolithus tinctorius is a mycorrhizal fungus that is not at all picky about its plant and tree partnerships. For this reason it is frequently used by foresters and gardeners to assist plant or tree growth (for impressive photos of plants and trees grown with and without the mycorrhizal support of fungi, see Mycelium Running, by Paul Stamets [2005]). It also grows well in poor soil, sandy areas, and so on, making it an even more valuable fungus for plant life."
Cut Surface - Mark Bower
In spite of the Horse Dung Fungus name, the cut surface of the fungus is actually quite beautiful, that is before it gradually transforms to what you saw above.  The cut surface shows pea-sized spore packets in gelatinous structure that will break down to brown dusty spores for wind dispersal.  The odor goes from fragrant to foul in maturity.  (Hey, what did you expect from a fungus named "dung"?)

My lurid fungus, Boletus luridus has now been renamed Suillellus luridus, just to make researching it more interesting.  There is much more than either of us wants to know about this mushroom at this Wikipedia link.

So what does this fly have in common with the story?  It is a horse fly (not to be confused with the horse dung) and we became blood "brothers" during the hike above as described in another blog.

Monday, August 21, 2017

Raising Imperial Moths

We have had a number of Imperial Moths come to our deck light the last few weeks.  As usual, most of these are males with their big feathery antennae sniffing for wafting female pheromones.  We did manage to find 3 females and as expected, they immediately started laying eggs in the paper bags that became their new homes.  Mary Bennett also found some eggs and all told we are raising over 240 eggs.

Imperial eggs with ballpoint pen - REK
The Imperial Moth, Eacles imperialis is one of our beautiful giant silk moths.  The thought of putting a newly fertile female in a paper bag for a few days may sound cruel, but since her role is to reproduce, I think we are doing her a favor.  In nature, her larvae must emerge and take their chances with predators that are looking for them and a variety of parasitoids can lay their eggs on the caterpillars.  We are protecting her brood and feeding them.

Imperial eggs day 15 - REK
Adult silk moths lack a digestive tract and don't eat.  Having mated, the female searches out a spot to lay eggs where the larvae will be able to find food.  She lives only long enough to meet her biological imperative.  The eggs are glued to a leaf  where they develop over two weeks.  Then they turn from clear to yellow, beginning to show the caterpillar curled up inside.*  They start to chew the inside of the eggs slowly, obtaining nutrition and eventually their freedom.  The first instar will soon emerge and start to wander around, frequently with the empty egg chorion shell still attached.

Riding a petiole - REK

The caterpillars feed on a variety of conifer and deciduous trees.  Our caterpillars have been munching leaves of maple, sassafras and sweet gum.  We are raising them in plastic containers with tissue or coffee filters on the bottom for convenient emptying of their frass.  They are not naturally gregarious but don't seem to mind the company.  That is a good thing as with 180 eggs to go, we can't provide individual boxes.

Imperial moths are univoltine, meaning they have just one brood a year.  The final instars will be provided soil and leaf litter to crawl into where they will form their cocoons.  They will spend the winter in the garage and come out to the Butterfly House in time to emerge for the Butterfly Festival.  Then I suspect there will be a several wild and crazy nights in the trees at the Springfield Botanical Gardens.

9-14-2017 Note
Its just frass.
As a reformed gastroenterologist, I couldn't help but notice that as they are in the 3rd instar, all their frass (poop to my younger readers) has a distinctive shape, looking like short corn cobs that were over cooked.  OK, waaay to much information but I just had to share it.

*You can see the action in the eggs, the caterpillar chew its way out and eat its shell in this Youtube video.
More at

Friday, August 18, 2017

Rove Beetles

Rove beetle, 12 mm Philonthus caeruleipennis - REK
I recently encountered two different species of rove beetles, members of the Staphylinidae family.  This is the largest beetle family with over 63,000 species worldwide, an ancient lineage that has been around since the Triassic 200,000,000 years ago.  Question, where do you find someone to count 63,000 species?  I suspect it is graduate students.

Earwig, note pointed cerci - Wikipedia
Rove beetles most obvious characteristic is their short wing covers (elytra) that don't reach the lower half of the abdomen like other beetles.  They resemble earwigs until you notice they lack the pointed cerci pincers at the end of the abdomen.
Ventral view of Philonthus caeruleipennis - REK
They can range up to 1.4" but most are less than 0.4".  Both of my species measured 0.5" (12mm).*  Most of the common species live in decaying plant and leaf litter, under stones and bark or around the margins of streams and bodies of water.  The Philonthus caeruleipennis pictured above was found in a decaying Oyster Mushroom, a common association for the species according to Eric Eaton.  It is commonly found in forest, marsh and prairie litter (often riparian), and sometimes under the bark of logs.

Typically rove beetles have short elytra covering small wings that are seldom used.  Many have evolved to be flexible, able to used their narrow bodies to crawl into narrow places or to shorten their bodies to reduce their surface area to avoid dehydration.  The increased exposed surfaces and junctures in their body means they lose moisture more rapidly.  They overcome this by staying under humid detritus, leaves, and bark.  

Gold-and-brown Rove Beetle (Ontholestes cingulatus) - L Bower 
The advantage of hanging around for millions of years is the time to evolve to live in a wide variety of niches.  There are a wide variety of shapes and colors as demonstrated by Linda Bower's find to the right. 

Specialized lifestyles means that they can lose some now redundant body parts and save the energy needed to grow and use them.  Some species that live in soil and caves have lost their eyes.  Others no longer need long distance transportation to maintain their species and no longer have wings.  

As you might expect with such a large number of families, there is a wide variety of foods that various species specialize in.  While many are saprophytic including fungi feeders, others are predatory (fly larvae and even mosquitoes) and a few eat only plants.  To get even, the Laboulbeniales order of fungi are obligate ectoparasites, living on rove beetles, mites and millipedes.  They get their nutrition from the animal while not usually causing significant harm to the host.

Rove Beetle - Homaeotarsus sp.
My other rove beetle can only be identified down to the Homaeotarsus genus and even to that level I can't find any more details about its lifestyle.  With 63,000 species in the rove beetle family I suspect it will be some time before all of them get fully studied, more work for future graduate students.

Movie monster or rove beetle? - REK
* I hope that the metric conversions don't bother you.  Most scientific articles use metrics so if we are going to continue to read about nature, we need to get used to it.

The University of Florida has a good in depth discussion on rove beetles in this PDF.

Wednesday, August 16, 2017

Walnut Caterpillars

Walnut Caterpillar, Datana integerrima  - Mort Shurtz

D. Integerrima in mass - Missouri University Extension
A while ago Mort Shurtz sent me this picture of a Walnut Caterpillar, Datana integerrima, that he found in his back yard.  When a moth species' common name is for the caterpillar, it means either that the cat is beautiful or obnoxious.  D. integerrima falls into the obnoxious category.  In their big years they tend to cover the trunks in large numbers, defoliate the trees and generously spread their frass around. 

Walnut Caterpillar Moth, Datana integerrima - Bob Moul
Although we have planted over 500 walnut trees in our riparian area within sight of our house, I have yet see Walnut Caterpillars on our trees or to photograph a Datana integerrima along Bull Creek.  At first glance it would be hard to guess that it was a moth or even would be capable of flight.  Its color is more handsome rather than pretty, more like a fine piece of wood furniture.  It has an orange fuzzy head and a black spot on its thorax.

Spotted Datana Moth - Datana perspicua
We commonly see its cousin coming to our deck light overlooking Bull Creek.  The Spotted Datana, Datana perspicua, has a similar color and shape but logically enough has a dark spot on it dorsal wing as well as sharper lines on its wings.  It feeds on sumac that is plentiful in the valley.

Yellow-billed Cuckoo - Joe Motto
Texas A&M cites some species of  wasps and flies that consume egg masses and larvae of Walnut Caterpillars, and many other insects and spiders prey upon larvae.  When disturbed, the caterpillars drop to the ground on a silk thread.  Birds don't make most of the lists of known predators and I suspect the fuzzy hairs of the Walnut Caterpillar serve as a deterrent.  I doubt that their large family gatherings would be possible if they were tasty and convenient for birds to eat.  Our Yellow-billed Cuckoo Coccyzus americanus, is the only bird listed as eating them, first reported in 1922.

Eastern Tent Caterpillar
Fall Webworm

Fall Webworms and Eastern Tent Caterpillars are other moth species that form large communal nests early in life that would seem to offer a feast for birds.  They appear to be protected by their web, until we tear it up exposing the individual caterpillars.  The masses of caterpillars that "flock" together can serve as a defense only if a bird eating one will decide that they aren't tasty, either because of chemicals or the nasty effects of the hairs.  But where potential food congregates there is usually some predator that will develop a strategy for getting it.

Lisa Berger sent me some information about one predator, the Black-billed Cuckoo, Coccyzus erythropthalmus that specializes in these species.  The Birds of North America information on the cuckoo's digestion of caterpillars is well worth a read.
"The Black-billed Cuckoo is a notorious consumer of caterpillars, with a demonstrated preference for noxious species, including the eastern tent caterpillar (Malacosoma americanum), fall webworm (Hyphantria cunea), and larvae of the gypsy moth (Lymantria dispar). Observations of cuckoos consuming 10–15 caterpillars per minute are testimony to the great service this species provides in forests, farms, and orchards. Stomach contents of individual cuckoos may contain more than 100 large caterpillars or several hundred of the smaller species. The bristly spines of hairy caterpillars pierce the cuckoo's stomach lining giving it a furry coating. When the mass obstructs digestion, the entire stomach lining is sloughed off and is regurgitated as a pellet." Excerpted from The Birds of North America Online.
This cuckoo species is rare in the Ozarks and therefore not an answer to our outbreaks.  Birds of North America's map shows that we are just barely in the southern edge of its breeding territory.  That still leaves our Yellow-billed Cuckoo.  According to Allaboutbirds, "Yellow-billed Cuckoos forage slowly and methodically in treetops for large, hairy caterpillars.  (They) are among the few bird species able to eat hairy caterpillars. In the East they eat large numbers of tent caterpillars—as many as 100 in one sitting."

Yellow-billed Cuckoo in the treetop - Clark Creighton
When disturbed by a potential predator D. integerrima drops rapidly to the ground.  Since the cuckoo tends to forage higher up, the caterpillar can start the long slow climb back up the tree while the bird has had its fill of its siblings and leaves, ensuring the survival of the species.  But how does the cuckoo handle the hairs?
"Cuckoos and hoopoes (Upupidae) are also able to clean larvae from their setae by rubbing them on the ground (Payne, 1997;Kristin, 2001), but the best adaptation to feed on hairy caterpillars is found on several cuckoo species. In these species, the gizzard inner layer has evolved towards a soft, thick and non-keratinoid structure that allows the larvae setae to be kept inserted in the gizzard wall and to be regurgitated as mixed pellets of mucous membrane and setae (Gill, 1980)"  Birds as predators of the pine processionary moth.
If that doesn't sound very appealing to you, watch an Asian cuckoo in action in this video.  It rubs the caterpillar along the branch to wipe off most of the hairs as well as drain the intestinal contents before eating it.  No wonder we call them cuckoos!