Thursday, October 27, 2016

Bumble Bees in our yard in Jonesboro, summer 2016

For a long time we have wanted to get interested in studying bees, but they are notoriously difficult to identify and there must be some 3000 species in the United States. But we decided if we started with one small, relatively easy to identify group, it might be a way in, and our friend Herschel Raney suggested we look at bumble bees this year, and they seemed perfect. So in 2016 we became seriously interested in the bumble bees that visited our garden. (We knew nothing at all about them.) We had a guide to identification (Bumble Bees of North America, Thorp et al.,[2014]), and as our first step we checked their distribution maps to see what species were possible in our area. Here is the list we came up with:

Bombus bimaculatus, the Two-spotted Bumble Bee
B. griseocollis, the Brown-belted Bumble Bee
B. vagans, the Half-black Bumble Bee
B. auricomus, the Black and Gold Bumble Bee
B. pensylvanicus, the American Bumble Bee
B. fraternus, the Southern Plains Bumble Bee
B. impatiens, the Common Eastern Bumble Bee
("pensylvanicus," by the way, is the correct spelling. It's just something that happens when you latinize a word.)

We had beds of flowers designed, over the years, in such a way that when one group of flowers finished blooming, another flower series would take over,  so that we had almost continuously blooming flowers. This was designed to attract butterflies, but it now also turned out to attract a continuously changing suite of bumble bees. By the time the first bumble bees showed up in early June, the pink phlox flowers were up, terrific for long-tongued moths and butterflies, but with their single deep narrow holes to the nectaries, they did not attract a single bumble bee. However, the pink coneflowers with their daisy-like flowers, each flower with an abundance of florets, and, in our pond, pickerelweed, with spikes of purple flowers, so that in each case a bumble bee could visit several nectaries by crawling around, without having to take off with its heavy body and land again, were both very attractive to bumble bees. At first we had mainly Bombus bimaculatus, Two-spotted Bumble Bees. I assumed the two black squares on the sides of the second abdominal segment were the source of the name, and these made the species easy to identify. ( I have recently read it is because of the two yellow spots, so now I’m not quite sure where I am.) Anyway, here is the Two-spotted Bumble Bee.

Most bumble bees are more or less alike, except with different patterns of black and yellow. So let's take this picture to orient ourselves, and see marks we need to see to identify the different species. Starting from the front, we see that this one has yellow at the top of the head. Some species have yellow at the top of the head, some have black. Next, we see that the thorax is completely yellow. Some species have a band of black over the top of the thorax, or black on the sides of the thorax. Different species have different segments of the abdomen black or yellow. On this species the belly is black, but the upper half of the first abdominal segment is yellow, and the second abdominal segment is yellow in the middle, but black along the sides, and then the remaining five segments (seven segments altogether) are black. Here it is now from the back:

The black spot is frequent in the center of the thorax on top. It is usually a sort of bald spot.

This was the first of the seven species we might see, and at first it was the only bumble bee around. It was particularly common on the dense bed of flowering pickerelweed in our pond. But occasionally we would see a Brown-belted Bumble Bee in the pink coneflowers out in the front yard.

This species similarly had yellow on top of the head and an all yellow thorax, and the first abdominal segment yellow. But the second segment was brown or at least brownish.

 And also occasionally we saw the Half-black Bumble Bee.

And once more, in this third of seven possible species, the top of the head was yellow, and the thorax was completely yellow. But in this case, the first two segments of the abdomen were more or less yellow, and the following segments were black, though with lengthy yellow fringes.

But with individuals with more modest fringes, it was easier to see why the species was called the Half-black Bumble Bee.

Then there was a change. The Two-spotted Bumble Bee became increasingly scarce, while a new species appeared. This one was very natty and quite different from the others. The front half of the thorax was yellow, the back half black, a broad black band pulled over the top. Two or three segments of the abdomen were yellow, then the last four formed a solidly black end.

This fit the pattern of B. auricomus, the Black and Gold Bumble Bee, and so that was what we called it, the fourth of our seven possibles.

Now the basket flowers were blooming out in the front yard, and we got a new species.

On this one, the back half of the thorax was black, the sides of the thorax were black, and all the segments of the abdomen were yellow, except the very last, which was dingy. Now we had a problem, because two species seemed to have that pattern, B. pensylvanicus, the American Bumble Bee, which was common everywhere, and B. fervidus, the Yellow Bumble Bee, which was common almost everywhere, though the range map did not quite touch our region. We went back and forth on this for quite a while until we remembered that other field mark. B. fervidus had yellow sides to the thorax, while pensylvanicus had black, and on ours we could see the black clearly. So pensylvanicus was the fifth of our seven possibles.

But then we found another problem. In the cup plants, also very popular with bumble bees, which were taking over from the fading basket flowers, we began seeing bumble bees marked like this:

This was the pattern of auricomus, the Black and Gold Bumble Bee, but something was not quite right. When we checked carefully through the descriptions of the various bumble bees, we discovered that pensylvanicus had an alternate pattern that looked exactly like this. This was confirmed for us when we were lucky enough to see a male pensylvanicus in the typical pattern mating with a female (a queen, that is to say) in this new pattern.

So these were pensylvanicus in a new pattern. But what about those first ones we saw? Were they Black and Gold? Alas, we remembered another field mark we needed to look at. The Black and Gold Bumble Bee has yellow on the top of the head; pensylvanicus has black, and that meant black in both of its color patterns. We checked all our photographs, and where the top of the head was at all visible, they were all black. We eliminated Black and Gold from our list, and now we were back to four of our seven possibles.

We felt much better however when, for one day only, we had a visit from a very handsome new species, Bombus fraternus, the Southern Plains Bumble Bee.

This one, in very clean black and pale yellow, had the first two segments of the abdomen pale, the rest black, and had a very slim black band over the back of the thorax just between the wings. So we now had five of the seven possible. We decided we weren't going to get Black and Gold, but we thought we were still likely to get the last one, B. impatiens, the Common Eastern Bumble Bee. We waited day after day for it to show up. The season was moving towards fall, however, and all of our seasonal flowers were coming to an end, and it didn't seem like any were left to come to serve as an attractant. Our scraggy weedy goldenrod plants, off in an untended corner of our yard, had not come out yet, but they didn't seem like they would draw in any bumble bees when they did.

That was the situation when we left to go to Arizona to see our brand new grandson.

Three weeks later we returned to find the goldenrod in full bloom and crawling with Bombus impatiens for a nice finish to the year, six out of the possible seven, not too bad for one garden.

B. impatiens (the name comes from the Latin name of a flower it particularly favors, jewelweed, though evidently goldenrod will work in a pinch) has yellow on top of the head, yellow thorax (with a particularly large bald spot), first segment of the abdomen yellow and the rest black.

I read now that the favorite habitat of B. auricomus, the Black and Gold, is not the garden, but open fields and farmland. That's where we will be looking for it next spring.

Wednesday, September 28, 2016

Paying attention to detail

We went out to our son's house in Tucson to see our brand new (and first) grandson.  I know this is mainly an insect blog, but I hope I can be excused this single mammal photograph.

Actually, I'm going to go on and discuss another vertebrate animal, a bird.

Cheryl was there to help out with the new baby, and my job was, essentially, to stay out of everyone's way. It was still summer and their bird feeders had not been in operation, but it was late summer with birds beginning to move around, so I started things up by filling a finch feeder with niger seed.

I spent a lot of time out on the back porch watching the insect, spider, lizard activity, and, when they arrived (almost immediately), the birds at the feeder. This was one of those diabolical feeders that would only offer food to desirable Lesser Goldfinches, leaving the over-abundant House Finches out in the cold (not a good metaphor when the temperature is in the 90's).

The way it works is, instead of the holes being above the perches, the holes are below them, and they can only be accessed by hanging upside down, which in theory only the goldfinches can deal with. It more or less worked, though there was a male House Finch who mastered it, and came regularly.

Where we live in Jonesboro, NE Arkansas, we have American Goldfinches, a related but different species. The Lesser Goldfinch is a western bird we only see when we come to Tucson, so we are not overly familiar with it. I remembered reading at some point that the Lesser comes with its back in two color forms, though I couldn't remember what the two colors were, or how the two species were distributed.  So I got out my Sibley and read "adult males in southern Texas are black-backed; frequency of green-backed adult males increases north and west to near 100% west of New Mexico." We were west of New Mexico, so 99% of the adult males here should be green-backed.

The theme of this blog is paying attention to details and here was a detail I had paid no attention to and I had never even noticed the back color of these birds. So I looked, and sure enough, the males were all green-backed.

And then virtually the next bird I saw was black-backed.

And what a beautiful bird it was, and if I hadn't been paying attention to details I would have missed it entirely, and so I would have missed this lovely 1% rarity (though it occurs to me I must have not paid attention to them by the million in South Texas, where we often go, and where they are common).

Here's another example of learning new things by paying attention to detail. In our backyard in Jonesboro there is a sugarberry tree, which is closely related to hackberry trees. In fact, Hackberry Butterflies lay their eggs on it, just as they do on regular hackberries, and we raise Hackberry Emperors by the score, a pretty orange and black butterfly. In our son's backyard there is, similarly, a hackberry tree, and it is covered with identical looking caterpillars, and eggs laid by an orange and black butterfly which is virtually identical, the Princess Leilia. When we are in Arkansas, in the east, we know we are seeing a Hackberry Butterfly, and when we are in the desert southwest, we are seeing Princess Leilia.

So here is Princess Leilia laying eggs in the hackberry tree in my son's backyard in Tucson.

As I was taking this picture, a revelation came to me. This butterfly is one of a group of butterflies called Emperors, the Hackberry Emperor, the Tawny Emperor, a few others, and here, because a butterfly with a feminine name can't be an emperor, its name is Empress Leilia, and always before this I had mistakenly called it Princess Leilia (probably confusing it with the heroine in
Star Wars). Unfortunately I still automatically call it by the wrong name, but this was only the first of my errors of poor attention to details.

I opened my book, Butterflies of Arizona, A Photographic Guide (2001) to p. 208-9, and learned that the Hackberry Emperor and Empress Leilia occurred side by side (in other words, the Hackberry was not strictly eastern), and the details had to be studied very carefully to tell which was which. A first tip was, Empress Leilia laid its eggs in Desert Hackberry, and Hackberry Emperor laid its eggs in Netleaf Hackberry trees. I asked our son's wife (a tree expert) what kind they had, and she said it was a Netleaf, and I learned to my surprise that what we had in their yard were Hackberry Emperors, just like ours back home. So how do you tell them apart?

Let's take another look at the Hackberry.

If you look just to the left of the head (or just to the right of the head), along the front of the wing, there is a pale orange panel with two small dark spots on it, then, towards us a little way, a longer thin curved spot, a little bit like a smiley face. Those three spots make this a Hackberry Emperor. This is the one in our son's backyard. Note the egg-stuffed abdomen.

Then when we went out in the desert, in the vicinity of a Desert Hackberry tree we saw this one:

Now instead of having three little spots along the leading edge of the wings it has two bigger spots, with a pale creamy area between them. This is Empress Leilia. Here are the two close up.

Let me give just one more kind of interesting example of paying attention to details, and this creature is so tiny, 2-3 mm, you can barely see it at all, let alone its fine details. But the marvel of digital cameras helps out, to blow the picture up to visibility. In this case we are looking at mosquitoes in the genus Aedes, the genus that is so much in the news lately. Here is the one we have at home in Arkansas

It is Aedes albopictus, the Asian Tiger Mosquito. It's a very tiny mosquito, about half the size of most mosquitoes, looking like not much more than a black dot on your skin. It is quite handsome with its black and white leg bands and the white spots on its abdomen. It tends to bite during the day (morning and late afternoon). Besides being annoying, this one, in the tropics, carries dengue fever, which fortunately is very rare here. Here is the detail: Note, easier to see on the second view, a broken white dash going across the back of the thorax. Then, in front, a white stripe going down the center of the thorax.

When we got to Tucson, we found a different Aedes.

It is the same in all respects, except it doesn't have the white stripe down the center of the thorax. This is the notorious Aedes aegypti, the transmitter of the Zika virus. The mosquito seems to be established across the southern border of the country from Florida to California. So far, except for a couple of spots in Miami, there is no Zika virus around for it to carry, but naturally it is being closely watched.

Sunday, August 7, 2016

100 Common Insects of Arkansas and the MidSouth (continued)

As you can see by the new title for our insect book, it has gotten longer and covers a larger area. We kept seeing creatures we wanted to add. It's probably over a hundred now. Cheryl is helping me clean up syntax, and especially, when I hit something I don't know, making sure I do some research instead of, as I usually do, making up an answer. As Huck said, it's mainly true with a few stretchers.

Wheel Bug, Arilus Cristatus

This insect is in the order Hemiptera, or "the true bugs." Colloquially, all insects are called "bugs," but technically, the true bugs are only those in this order, and are marked by having the basal half of the forewings leathery and the outer half membranous, a segmented beak that folds under the chin when not in use, and they do not have complete metamorphosis, hatching out of the egg more or less like a small version of the adult. Some use their beaks to suck plant juices, some to suck the juices of their prey. The Wheel Bug is one of the latter.

If you have a garden (that you don't pour a lot of poisons into), you will be sure to have seen this big (over an inch long) bug with what looks like a half saw-blade on the back of its thorax. The long beak looks formidable and it really is. If you try to pick it up and it gives you a jab it will make you yell. They use it to kill their prey (chiefly caterpillars) and turn the insides into soup which they suck dry. I don't mean you should be stamping on them, I mean you should be admiring them as powerful actors in the natural system around you which needs a balance between survivors and population controllers.

Eight-spotted Forester, Alypia octomaculata

Here is a very handsome and commonly seen day-flying moth. Most moths are secretive, but this one WANTS to be seen. Black white and red is a color-scheme well known throughout nature, to birds, lizards, insects, spiders, even human beings (think of bees and wasps: we see black and orange or black and yellow bands, and we know not to touch). These are warning colors; it's technically called aposematic coloration. Some combination of black and white and orange-red means "Don't touch me, I have a nasty bite, or an envenomed sting, or I taste terrible to the point of being poisonous." Sometimes they are just pretending with their colors, and can't hurt you or don't taste bad, but who wants to take the chance?

Bald-faced Hornet, Dolichovespula maculata

These make the basketball-sized paper nests hidden in bushy foliage (only coming into view when leaves are lost in autumn). I remember finding a nest in mid-winter (the inhabitants presumably dead and gone) and bringing it home and setting it attractively in a corner of my study, only to learn, when the room had warmed up to spring-like temperature, that a couple of dozen pregnant queens waiting for next year were overwintering in the nest and were now all emerging early and in very bad tempers.

These hornets are meat-eaters and the workers go out and catch horse flies or butterflies or whatever insects they can and tear them up in pieces and bring them back to the nest. They have a special trick. On cold mornings they can, by shivering, warm themselves up to mammal-like temperatures. They then go out and look for insects that are too cold to fly away. You can see them flying along and smashing into every black spot they see on a leaf, in case it is a tasty insect.

(I didn't realize until I put that picture up how much it looked like a gorilla wrapped to be a mummy,)

Paper Wasp, Polistes metricus

There are several species of Polistes paper wasps. You might see them early in spring scraping fiber off smooth wood or plant stocks, which they mix with their saliva and make into a heavy gray paper, called carton. With it they make the pizza-shaped open nests that are hung from foliage, or often under the eaves of your house. There is a large all red species (P. carolinus) which I prevent from nesting around our house, since they tend to attack us, but the others (with various patterns of black, yellow, and red) are inoffensive and we enjoy watching them develop. The nest here is in an early stage. The over-wintered pregnant queen started this nest by herself and raised the first few workers. This is the perilous time and many nests fail, but she has made it through. Up near the top of the picture you can see eggs inside the cells, and a newly hatched grub. Below, a fully developed grub is spinning a cocoon around itself. Then there are three closed cocoons developing. The dark smudge at the top of the nest is the queen herself, resting on the stem that supports the nest. She no longer has to risk her life going out and foraging. Her job now is to stay there laying eggs while the others bring caterpillars and other insects to feed the babies like birds in a nest. There may be fifty or so workers by the end of the season.

Paper Wasp, continued, Polistes exclamans

Here is a mature nest in September. It looks to me like the flight deck of an aircraft carrier, ready for combat. When I got under the nest, which is in the eaves of the house, they all snapped to attention, and if you look you can see almost every one is staring straight at me. This is a peaceful species, but I didn't go any closer.

Paper Wasps, Polistes spp. (continued)

At the end of the season the queen and all the workers will die, but before they do they begin producing males and virgin queens. As it starts getting colder the virgin queens begin looking for sheltered places to hibernate in, hollow logs or, particularly, insides of buildings, attics or openings in the eaves. As they find these places, it turns out the males (identifiable by their white faces) are already waiting to waylay them and won't let them in till they have mated. The males then die, and the pregnant queens winter in the shelters, then emerge the following spring to start a new generation.

Friday, July 1, 2016

75 Common Arkansas Insects (continued)

False Crocus Geometer, Xanthotype urticaria

I don't know what these attractive moths have done to deserve their notorious name. And, to tell the truth, I don't know anyone who has seen a genuine Crocus Geometer. But whatever the false one's personal morality, it is an often seen, pretty, day-flying, almost always mating moth. Once you spot a pair lying in the grass at your feet, you will not forget it, nor, once you hear it, will you forget its unfair name, associated as it is with the basest treachery.

Rock-loving Grasshopper, Trimerotropis saxatilis

Grasshoppers, with a few exceptions, are the grazing animals of the insect world, the things that everything else eats. Therefore evolution has pushed them, not towards better weapons, but towards better evasion tactics. Camouflage is one of them, and this grasshopper is one of the supreme examples. It flourishes on lichen-covered limestone glades, its pattern imitating the shapes and colors of the lichen to perfection. People who have noticed this grasshopper spontaneously call it "the lichen grasshopper."

Fruit Fly, Rhagoletis sp.

Another (and very common) defense for a weaponless creature is to pretend to be something dangerous. Here is a particularly clever example: The wing markings make this look astonishingly like a jumping spider, a very fierce big-game hunter, walking in the other direction. In fact when being stalked by a jumping spider this fly has been seen to walk backwards towards the spider, actually making the spider back off and seek some other target. Here is a typical jumping spider for comparison.

Striped Hairstreak, Satyrium liparops

There are half a dozen or so species of hairstreaks in Arkansas, small, pretty, fast flying butterflies that almost always land with their wings closed up above their head, so that you see the wings' underside. There are various patterns on the wings, but they usually feature large red or blue spots, and "tails" at the end of the hind wings. As a sort of nervous habit, they constantly slide their hind wings back and forth against each other with the effect that the tails seem to be waving up and down. The blue and red spots resemble eyes, the tails are very like waving antennae, and that's their trick. A spider or a bird that wants to catch a butterfly goes for the head, that being the quickest way to disable it. But mistaking the big eyes and the waving tails for the front end, they make their grab, and the butterfly escapes in the other direction. This has been photographed in the case of jumping spiders, and the back ends of healthy active butterflies often have a beak-shaped rip.

 Glowworm, Phengodidae, Phengodes sp.

Glowworms always sound like mythical beasts, something in soppy songs, but here one is, in the middle of a huge outbreak of flat-backed millipedes. This is the larval form of a beetle, and it could be an actual larva, but it could also be an adult female, which sexually matures, mates, and lays eggs retaining its larval form, only the male metamorphosing into a beetle form.

Another oddity: Millipedes are so poisonous nothing eats them, that is, except glowworms, and glowworms feed entirely on millipedes. Here is the glowworm attacking a millipede it is about to devour.

Of course, you have to see a glowworm at night to see its third oddity, from which it takes its name.

Sunday, June 19, 2016

75 Common Arkansas Insects

Most people don't seem to notice insects. If they do see one, there is first a look of revulsion, followed by a search for something to swat it with. I'm probably being optimistic, but I think if they had any idea how intricate and fascinating the life stories of insects can be, they might alter their attitude. I think anyway there are a lot of people who spend time out in nature, hikers, fishermen, gardeners, who notice things, and are at least a little bit curious about what they see. I'm contemplating writing a little booklet just for these people. If I can point out something to them that is commonly around, and is easy to recognize, and if I can tell them some little something of interest about it, maybe they will look at it a bit more favorably the next time they see it. This booklet (to be called 75 or whatever number I finally arrive at Common Arkansas Insects) will have a photograph of an insect at the top of each page, with a small paragraph about the insect beneath it. Here are some sample pages.

75 Common Arkansas Insects

American Carrion Beetle (Necrophila americana)

Don't confuse the name of this common species with that of the rare and endangered American Burying Beetle. But it is in the same lugubrious business: helping to clean up dead bodies. Its name Necrophila means 'lover of dead bodies.' When they get a whiff of a road-kill opossum or some other delectable, they head for it. They fly fast and directly, at about our eye-height, and something odd occurs. They are suitably black for their job, but note the yellow thorax with a dark patch in the center of it. This is the pattern of a bumble bee, with its fat black body and hairy yellow thorax with a dark bald spot in the center of it. When you see one of these beetles flying, you can't believe it isn't a bumble bee. I'm an experienced field biologist, and even I have to strain my eyes to see that it is actually a beetle pretending to be a bumble bee. It might make a bird hesitate to grab something out of the air if that something might have a formidable stinger.

Once it arrives at the kill it feeds on the abundant fly maggots, and lays its own eggs, and when they hatch, they begin feeding on the skin and dried bits of sinew the other scavengers can't handle.

13-Year Periodical Cicadas

Cicadas in general, found all over the world, are the large oval-shaped insects that sing and clank and zing all through the long hot days of summer. You see the empty skins of their nymphs clinging to the base of trees when you get up in the morning, but after that you only hear them, because the adults sing hidden in the tops of trees.

However one special group, the Periodical Cicadas, are easy to see just because there re so many of them. These harmless, but rather sinister looking creatures have jet black bodies, blood-red eyes, bright yellow veins on their transparent wings. Here's their bizarre story: The nymphs hatch from eggs laid in trees and burrow underground where they feed by sucking the juice from tree roots. All species of cicadas do this, and most emerge and change into adults in a year of so. But the Periodicals found in Arkansas stay underground for thirteen years, and then emerge in scattered places (each place well known to biologists) around the state. The populations are staggered so every few years some will come out somewhere. There are four species, and in May and June of 2015 all four emerged at once. If you looked up in the trees you could see them constantly flying out from among the leaves, as numerous as bees. Their high-pitched whining hissing sound could be heard, in places, for over a square mile. They had no fear or avoidance instinct. Birds and other animals could eat them all day till they were sick; there were still millions left, to mate and lay eggs for the next thirteen years. Within days the dead and dying began littering the ground. After a month they were all gone, not to appear again for several years.

An identical set of four species comes out every seventeen years, but none of these happen to occur in Arkansas. The two groups, 13- and 17-year, are found in scattered localities in the eastern United States, and nowhere else in the world.

Hanging Thief, Diogmites sp., Asilidae, Robber Flies

Unless someone points them out to you, you are likely to overlook robber flies. There are over a hundred species in Arkansas in all sizes (from 3 mm to 50 mm) and shapes (they often mimic wasps or bees, especially bumble bees). They are powerful charismatic predators, in fact each is the alpha predator in its particular ecological community. Once you get your eye in for them, you will see them sitting at the tip of a twig, or on a bare patch of ground, with an unobstructed view of the sky, and suddenly they will fly up so rapidly they seem to vanish, only to reappear at the same spot an instant later, this time carrying some insect they have just snatched out of the sky. They fly up like falcons, wrap their long spiky legs around their prey (often wasps or other dangerous creatures, even other robber flies), stab it with their beak loaded with neuro-toxins and digestive enzymes, and return to earth to suck its juices. Those like this one, in the genus Diogmites (sometimes called "hanging thieves") have the habit of getting under the foliage and hanging by their forelegs to eat their prey. You can recognize them by this behavior.

Robber flies have these features in common: widely separated eyes for good depth perception, a sharp beak, a sort of beard or mustache above the beak, which is thought to protect the eyes during encounters with dangerous prey, and long muscular spiky legs with hawk-like talons at the ends.

Hanging Fly

Here is another kind of predatory hanging fly. This one is a member of the Scorpionfly family (Panorpidae), and is much less formidable than a robber fly. It's a spindly creature looking rather like a crane fly, but has its own novel way to capture its prey. The male, pictured here, like the Hanging Thief, gets down low in the foliage and hangs by its front legs. But look at its hind legs danging below it, with their complicated spiny feet. They are like loaded mousetraps, and if a moth or other soft creature in its flight brushes against these feet they snap around it in a flash.

The Hanging Fly is not hunting on his own account. The female will not allow him to mate with her unless he presents her with a meaty gift to eat while he is doing so.

Mantises catch prey with their predatory front legs, robber flies catch prey by wrapping all six legs around it. The hanging fly is one of the very few I can think of that catch prey with their hind legs.

Braconid Wasp sp., Genus Cotesia

Sometimes something white down in the shrubbery will catch your eye. When you bend down and look, you will see a stationary caterpillar with up to a hundred tiny white cocoons clustered on its back, or sometimes in a tidy stack underneath it. It has been parasitized by a tiny (5 mm) Braconid wasp which has used its ovipositor to inject dozens of eggs inside the caterpillar's body. The wasp larvae have devoured the caterpillar from inside, eating non-vital tissues at first, so that the caterpillar could continue eating and growing, but now to feed them, not the moth or butterfly it might have become. When they were ready, they punched their way out and spun their cocoons. The caterpillar may still be alive for a while, but hasn't the energy left to make it own cocoon.

It's a common fate for caterpillars, but actually the wasps are the heroes here, the great controllers of population. Without them, and the migrating warblers and other carnivores, caterpillars would overrun the world, eat everything green, and bring down their own environment.

What do you think? Should I go on with it?

Thursday, May 12, 2016

Sweating the SMALL small stuff

Everyone, I expect, knows about the guy (his name now forgotten) who said the key to a stress-free life is, Rule 1: Don't sweat the small stuff, and Rule 2: It's ALL small stuff.

He was a genius, and I try to live by those rules. But when I came to write a blog that would concern itself mainly with insects and other small creatures, I called it "Sweating the small stuff," and thought that was rather clever, until I looked into it and discovered about forty people had already used that name for their blog.

Anyway, lately we seem to have been looking at smaller and smaller stuff. It started when I got a new camera and macro lens set-up, a step up from my last one, and to try it out went around the garden taking pictures of every small thing I could find. It started with this honey bee, coming to a spiderwort.

 I downloaded this picture, then put it to the test: I blew it up until just the bee filled the whole frame.

I was very pleased that the image could keep so much sharpness after being enlarged so many times.

Then (I was out with Cheryl) we saw a tiny thing that looked like an ant trundling along. If the bee was, let us say, 10 mm long, this new thing was closer to 5 mm long. When we looked really closely, we saw it was actually a jumping spider mimicking an ant. Here it is blown way up so you can see it more clearly.

An ant has six legs and a pair of antennae; a spider has eight legs and no antennae. But this spider is walking on its back six legs, and is waving its front legs in front of it to simulate antennae. Very clever, but why would a tiny spider imitate an ant? Well, ants are full of formic acid, which means they don't taste very good, so most things leave them alone.

Anyway, to get on with small things, Cheryl has an old pot in the front yard full of radish seedlings, and with her sharp eyes spotted some things in them that she had to point out several times before I could see them. Here's the pot. If you look carefully, you might see some little whitish dots sticking to the stems.

Here, from closer up, is what Cheryl saw.

We knew what these were right away. The pot had been overrun with aphids, but now the aphids were virtually wiped out. Tiny parasitic wasps (we're talking really tiny now, 1.5 mm) had visited them, and with their sharp ovipositors had injected an egg into each aphid. The egg hatched into a wasp grub, and the grub fed on the aphid. To show you how small the grub was, that aphid provided enough food for that grub to grow to full size and form a pupa (all this inside the shelter of the aphid's outer skin). While the grub was feeding, the aphid turned brown, which made it easy to see which ones had been parasitized.

Here is the scene several sizes larger. On the top left are two healthy juicy green aphids, on the right brownish ones that are harboring feeding or already pupated grubs. One has a round hole in the top, marking where a wasp had metamorphosed and chewed its way out.

Once we got our eye in, we noticed that the wasps were flitting all about. Making pictures and blowing them up helped us to see more of the action, though we are far from having everything figured out.

Here, for example, is one of the wasps.  It's possible that it just emerged from the hole in the aphid beside it.  Its fairly slender abdomen, its lack of an ovipositor, and its very long antennae make us believe it is a male. This is guess-work, but perhaps the long antennae are very sensitive to the alluring odors of females. Perhaps he can smell a female about ready to burst out of the aphid shell he is sitting on, and he is waiting around to make sure he gets first dibs. For the moment all the many wasps we see seem to be males, and perhaps it is timed this way to make sure each emerging female has a mate waiting for her. Otherwise it might be impossible for such tiny things in such an enormous world (millions of times bigger for them than for us) to ever find each other.

The wasps can't waste too much time sitting around, because they are themselves part of the stream of life, and are just right for slightly larger creatures to feed on. We see a half-grown jumping spider is already feeding on one.

Cheryl looks under a leaf that has spider webbing in it (her thumb and the nearby wasp will give you a sense of scale) and finds another spider that has a wasp wrapped up.

Perhaps you still can't see it; it's just down from the wrapped wasp, and a little to the left). It's not only minuscule, but has protective coloring. Here it is still larger.

Okay, one more try.

The next day a more serious threat appears. You know the big black and yellow garden spider that makes enormous webs in the corner of your yard. They are formidable hunters. Those that live over our pond feed mainly on tree frogs. Well, here's what they look like when they hatch from the egg, and they already have something magic in their web, ultra-violet coloring or something, because look how many wasps this one has caught in a single day.

And now we believe we have seen the most sinister predator of all.

We thought at first this was finally a female. Note the fat abdomen, the short ovipositor, the short antennae. But now we have seen it poking its ovipositor into the aphid shells. There is nothing inside those shells but the newly forming parasitic wasps. Besides, this wasp is marked differently from the male wasps. Is this a different species? Is this, in fact, a hyper parasite, a parasite upon parasites?

Who would have imagined a few shots with a camera and macro lens could open up a lifetime of studies.