bootstrap analysis

100 hungry mouths to feed

A couple years ago I lamented that I didn't see sillkmoths much anymore.That was the year our friend Dr. Steve gave us a couple of Polyphemus (Anthera polyphemus) cocoons, so we got to see (and release) the adults that emerged. Dr. Steve has a big piece of property nearby, and his brother owns a tree nursery. They are able to find and raise several species of silkmoths every year. This spring, they gave us a bunch of eggs, mostly Cecropias, Hyalophora cecropia, but also a few Polyphemus and some Lunas (Actias luna).

The latter is, I believe, one of the most beautiful insects in North America. In all my time in the field these past decades, I'd never seen one, even though at work we have abundant black walnut, one of their favorite larval host plants. I intended to raise all three species and release them at work, with the hope of augmenting very sparse local populations.

We started out with about 50 Cecropias, 15 Polyphemus, and 20 Lunas. I know that doesn't add up to 100, but as usual we were also raising some Monarchs, and Black and Giant Swallowtails. This year we're also raising some Carolina Sphinx (Manduca sexta). You know these as tomato or tobacco hornworms. Purposefully raising what many people still consider the scourge of their garden may seem really weird, but they seem to have been wiped out in this area and I'd like to see a few adults again. So yes, I have been raising over 100 caterpillars this summer (so far!).

Luna eggs hatching

The silkmoth ranch starts out innocently enough. Once the eggs begin to hatch, the tiny caterpillars are put in small groups in tupperware containers with damp paper towels and some leaves of their host plants. I raised the Lunas on black walnut, the Cecropias on box elder and lilac, and the Polyphemus on maple and dogwood. Everything but the walnut was available in the yard.

 

Cecropia eggs and newly hatched larvae.

Twice a day the containers have to be cleaned out and restocked with fresh food. This takes longer than you might think. It's pretty common to lose a percentage of young larvae to bacterial or fungal infections, mishaps, or parasitoids (if you raise them outside, more on them later). I was careful to make sure no frass (poop) was clinging to the tiny cats when I cleaned the containers. When they were all spiky little things only a few millimeters long, this required a soft brush.

They outgrow sandwich-sized containers pretty quickly, and graduated to plastic shoeboxes within 10 days. At this point, they were still stacked up all over my office.

The next upgrade was to aquariums and empty cat litter buckets in the garage. Food was kept fresh by inserting branches into plastic carry-out cups of water -- the lids with the holes for straws are perfect for holding the plants while not allowing the larvae to fall or climb into the water.

We kept some on the bench by the open window, and the rest we moved outdoors in dappled sunlight during the day, and back inside at night. It's important they get some light and be exposed to natural cycles of daylight. This, apparently, influences whether multi-brooded species will emerge after pupation the current year, or overwinter. At this point, fortunately, I was home on vacation, because it took about 2 hours a day to tend to all these things!

 

Cecropia cat, fourth instar.

The Cecropias in particular were voracious, and there were a lot of them. I think we only lost around ten. By the time they were 3 inches long, I took a dozen to work and let them go, hoping they'd fend for themselves. By the time they started spinning cocoons, they were the size of large sausages. This species is supposed to be single-brooded here, so we'll keep these cocoons overwinter and release the adults next year.

 

Polyphemus cats. There was much more variation in their individual growth rates compared to the other species for some reason.

We lost quite a few Polyphemus to some pathogen when they were still very small. Once they reached second and third instar, they had been moved to mesh-covered containers outside. One day, we found two very tiny wasps had made their way through a small opening in the mesh. They were some sort of female braconid wasp. These are common parasitoids of many types of caterpillars. Within days a few more Poly cats died. The remaining ones seem fine and are starting to spin cocoons, but we shall see.

 

Anybody get this to genus? I am reasonably sure from the wing vein pattern that it's in Family Braconidae.

We ended up with 11 Lunas spinning cocoons. I'd heard conflicting reports of whether they were double-brooded or not in Michigan; most people told me these would overwinter. But they were wrong. More in a later post...

this turd has legs

I haven't spent much time in the field this summer. The last 6 or 7 years, I've had summer field work tied to grants; this year, my grants involve sitting in front of the computer. But over the holiday weekend Kingfisher and I got out a bit to do some general exploring. At one spot, he called me over to look at this curious insect. At first glance, he thought it was a gall on a leaf...until it moved.

It turns out this is the larvae of a leaf beetle in the subfamily Cryptocephalinae, known as the casebearers. The case the larva is toting around is made from its own excrement, a good way to become unobtrusive and unappealing to predators while in a vulnerable state (I always say). According to the incredible book Insects: Their Natural History and Diversity: With a Photographic Guide to Insects of Eastern North America:

"Leaf beetle larvae in several subfamilies use their own excrement to form protective shields or coverings, but larvae in the subfamily Cryptocephalinae carry this habit to an extreme. The eggs hatch under a fecal blanket and proceed to use their own waste to make a case that is added to as they grow."

The adult beetles are quite attractive, reward for spending the beginning of their lives covered in their own crap. This one was feeding on Rubus, there's a possibility it may be Chrytocephalus venustus.

tiny-headed, beady-eyed, pointy-nosed running purple frog

This is awesome.

firefly watch!

Who doesn't like watching fireflies? Now you can contribute to a study on the distribution of fireflies via Firefly Watch, a citizen science project of the Museum of Science in Boston.

national pollinator week: what's on your flowers?

June 22-28 is the 2nd Annual National Pollinator Week, an event sponsored by the Pollinator Partnership. The fact that so many of the world's pollinators are in deep trouble is finally starting to make the news. There are, of course, many bats, birds, and other animals that perform pollination services. Aside from declines in those populations, people are hearing more about the problems with our most familiar domestic insect pollinator, the honey bee. There is a real crisis, too, with wild insect pollinators, especially bumblebees.

Reasons for declines in these pollinators include habitat loss/destruction/degradation and introduced pathogens and parasites. Pesticides are also a likely culprit, but unmanaged wild pollinators are relatively poorly studied in this regard, and there is a lack of historical baseline data to fully assess impacts of chemicals on various species. Another worry is possible loss of synchrony with blooming plants due to climate change.

Some great resources on pollinators and their conservation:

• The National Academy of Sciences released a status report on North American pollinators which can be read online.
• The Pollinator Partnership also has a great page of information.
• Your tax dollars at work: the National Biological Information Infrastructure pollinators web site.
• The Xerces Society's Pollinator Conservation Program.

People often forget that flies are important pollinators. Regular Bootstrap readers will recall that last year I began my "Diptera in the Yard" project, and that I think many species of flies are remarkably cool. In honor of National Pollinator Week, I thought I'd do another photo essay on flies, featuring some that perform pollination duties.

The family Syrphidae is huge and includes many lifestyles, but at least 1000 are known to be pollinators. You have most likely seen "flower flies" like this Helophilus fasciatus. This one is a female -- her eyes don't touch at the top. Male flies have bigger eyes that generally meet.

These horny little flies are also Syrphids, Toxomerus marginatus. Like most Syrphids, the larvae are predaceous; Toxomerus larvae feed on aphids or other small insects.

Most of the really good bee and wasp mimics are Syrphids (the top photo is of a bumblebee mimic, Mallota; there is another photo in my other post). However, the Bombyliidae are known as the bee flies. They are typically hairy and have a long proboscis. The most familiar bee fly is Bombylius major. Here are a couple of other bee flies. The first is this whimsical fly in the genus Geron.

 

And this is Aldrichia ehrmanii, a species which was recently very common in my area.

Tachinid flies are the ones that lay their eggs on butterfly or moth caterpillars. The larvae burrow into the caterpillar, feed on the host, and drill their way out when ready to pupate, killing the caterpillar. About 2000 species are known to be pollinators (the adults, that is). For example, the only place I've seen seen these Archytes tachinids is on flowers.

 

So starting this week, stop and take a look at the diversity of pollinators in your garden, your nearby park, and the empty lot down the street, and give them a little more appreciation for what they do and their role in the ecosystem.

Hey -- what's on your flowers?

random animal news

• I did not know squid beaks were one of the hardest organic objects in nature. Therefore, I was not mystified by the dilemma of how such rigid objects were efficiently attached to "blocks of jello." Mystery now solved. 


• Bats are dying left, right, and center from a mysterious virus that  may wipe out entire populations and species, and researchers are completely stumped. 


•  China does it again. Tibetan antelopes and the Qinghai-Tibet railroad do not co-exist peacefully. The photo that showed them in harmony was faked. I first read about this in the journal Nature, but Treehugger also covered in very well.

Squid photo by Hexion; bats by Tolka Rover.

wall of moths

As I was returning to my office after a bird survey yesterday, I found a number of small gray moths on the cinder block wall of our building. There were at least 30.

The pattern of the individual moths varied a bit, but they blended in really well with the wall. The wavy lines their wings would have been an even more perfect match for tree bark.

I took some photos, but know bettter than to be optimistic about identifying small, bark-colored moths. I wouldn't have bothered, except that I thought that their numbers and early emergence might be more characteristic than their appearance, and enable me to clinch an ID. I figured I might have some luck going to the moth section of BugGuide and browsing recently submitted photos.

I was right. I only had to click through 4 or 5 pages before I hit on a ringer: Phigalia titea, the Half-wing Moth (a.k.a. Spiny Looper, Eastern Oak Looper). It's one of the geometrid moths; the "inchworm" larvae eat a wide variety of hardwoods.



There are two other Phigalias that fly early in the season: P. strigataria (Small Phigalia) and P. denticulata (Toothed Phigalia). I took a second look at the walls today, and there may have been a few Small Phigalias in the mix, which are smaller, often darker, and tend to show less hing wing when perched.

I didn't find out anything really compelling about the natural history of these moths, except it was kind of interesting to learn that they were all males -- females are flightless and have only vestigial wings.

Despite their apparent ordinariness, I'm sure the early emerging adults are a really important food source for insectivorous birds arriving during this period of fickle weather. The eggs the moths are now laying will also provide a welcome protein source for bark gleaning species both resident and migrant, such as Brown Creepers, chickadees, and nuthatches. And of course, the larvae will be out just in time for the big wave of northbound migrants still to come, with some caterpillars left over for hungry nestlings.

On second thought, their role in the forest food web makes these modest moths anything but ordinary.


  

looking for bo'wings

Signs of spring are slowly unfolding here in the upper Midwest. Killdeer, grackles, and Turkey Vultures have returned. Northward-bound American Tree Sparrows are appearing at our feeders. And over the last few weeks, a number of surrounding counties have had reports of another northbound species, Bohemian Waxwing. This has been a great winter for them, as the mountain-ash berry crop in northern Ontario was poor, prompting them to move south. The last (and only) record for Bohemian Waxwing in my city was from 1945. I believe this was the only documented record for the county, too, until one was found in a flock of Cedar Waxwings in January in a Detroit park.

Having nailed down that one for a county record, I've been determined to find one in my city. I live very close to work, but have been taking one of several circuitous routes there and back daily, trolling as many of the crabapple trees that still have fruit as possible. About a week and a half ago, I found a few Cedar Waxwings in front of the local civic center, right around the corner from home. I thought this was a little odd, since the crabapples had all been stripped there. A few days later, a friend found a flock of nearly 100 in the same place. As it turns out, they were feeding on juniper berries.

The city landscaped this area about six years ago, and planted dozens of eastern red cedars (Juniperus virginiana); the photo shows just one portion of one row. They aren't very tall yet, most are about six to eight feet, but they are loaded with berries. The fruit take around 18 months to ripen. The waxwings are only eating the ripe blue fruit, and there are lots of pale unripe berries that will be next year's crop. In much of their range, juniper berries are a crucial part of the winter diet of Bohemian Waxwings. In some areas out west, Townsend's Solitaires feed almost exclusively on this fruit in the winter. That's another species I look for here every winter; it would be a first for the city.

So this is a twice-daily stop for me. My husband also checks on his way home, and my friend drives through once or twice a day. Sometimes there are only a couple of dozen Cedar Waxwings there, but we've often had up to 150. When they aren't gulping down fruit, they sit in the surrounding trees, digesting, preening, and twittering softly. Surely if a Bohemian Waxwing were flying by it would hear the gentle calls of its cousins -- which must include the murmurings of the happily sated -- and come down to see what all the satisfied contentment was about.

In the afternoon, I like to park and look through the flock carefully. A Bohemian would stick out like a sore thumb, being larger and grayer, with a russet-colored undertail. But the birds are not easy to see when they are tucked in the evergreens, and besides, the delicately elegant Cedars are a pleasure to watch. Compared to picking through a legion of gulls, examining a gathering of waxwings is a delight.

Over a hundred waxwings can make short work of even a substantial berry crop. Indeed, there isn't a whole lot of fruit left on these trees. It's also getting a little late for Bohemian Waxwings to be on the move this far south. My chances of finding one are getting slim, and it could be many years before they stage such a grand irruption to this latitude again.

Watching the Cedars, at least, has been no hardship. Plus we have discovered that these plantings will be, uh, a fruitful place to look for great birds in the coming winters. I'll be a little sad to see this opportunity fade away, but more than happy for spring to take over completely, bringing its own rich possibilities of discovery.

Top photo of a Bohemian Waxwing by ru_24_real; thanks for publishing under a Creative Commons license. All other photos made on a daily waxwing stop by my husband, Kingfisher. Thanks, babe.

hymenoptera in the yard

In August, I described my summer "project," to learn more about the flies, bees, and wasps in my yard.  I posted a series of some of the photos I took of the cool Diptera (flies) I was able to identify. You foolishly encouraged me to do more posts in this vein, so here I am, with some of the Hymenoptera (the order containing bees, wasps, and ants) I've found in the yard.

Above is a grass-carrying wasp, Isodontia elegans. Grass-carrying wasps are solitary wasps which provision their larvae with tree crickets (typically). They make their nests in hollow objects. Females snip blades of grass and line a nest cell with them. I've seen the all-black native species, I. mexicana, entering the hollow window bars of our campus parking structure, trailing grass behind them. They'll also nest in the furrows of window frames; homeowners may find the nests when installing storm windows in the fall.

This photo is the first taken in Michigan of I. elegans, an introduced species. The following year my entomologist friend Mark (also apt to find new records on his property) vouchered the first specimen, and we co-authored a paper. These wasps are as common as mexicana in my yard. It just shows you that you never know what you might find right under your nose if you look.

This small solitary wasp is Philanthus gibbosus, one of the species commonly known as "beewolves." As the name suggests, they are predatory, and prey on bees. They are quite abundant, but this is the only time I've ever seen one grab a bee. Lucky shot.

Two very large wasps in the genus Sphex are common at flowers in summer. One is the blue-black S. pensylvanicus. The other is this species, the Great Golden Digger Wasp, Sphex ichneumoneus . Digger wasps dig burrows for their nests, and provision them with crickets, grasshoppers, and katydids. Although imposing, they are not aggressive. I've never been stung no matter how close I've gotten for a photo.

Only a week after the first Giant Resin Bee (Megachile sculptularis) was discovered in northern Michigan (by my friend Mark's wife!), I colllected one at one of my study sites about 30 miles from my house. That same day, I came home and found this one in my yard. This species was introduced into the U.S. from Asia, with the first one being recorded from North Carolina in 1994. More info here. Another paper to co-author. I publish more stuff about insects than birds!

While we're on the topic of introduced species, here are a couple of interesting ones. Wool carder bees are leaf cutting bees. Most leaf cutting bees cut semi-circular holes out of leaf margins and use the pieces to line their nests, which are in burrows or cavities. Wool carder bees use the "wool" from felted plants (like lamb's ears). The species above, Anthidium manicatum, is introduced from Europe, purposely brought here as a pollinator.  Another species, A. oblongatum (below, in a photo I took at work), was introduced in 1995...I'm not sure if that introduction was intentional.

Finally, we'll wrap it up with one of the several species of bumblebee I've found in the yard, the Golden Northern Bumblebee, Bombus fervidus.  They are particularly soft and plush looking, and very fond of the zinnias!

I got to 42 species photographed and identified in the yard so far, and another 20 species nearby. I've a few photos I'm still working on. The asters are still in bloom in the extended summer weather, so I might find a few more before frost.  This was a really gratifying project that I'll continue next year. Now that I have learned to recognize many Diptera and Hymenoptera to family, I will probably be trying to photograph and ID some tropical species as well. My next opportunity will be January in Panama. Expect a tropical insect photo salon this winter!

a sheep in wolf's clothing

Eastern cicada killers (Sphecius speciosus) are big wasps. The "dainty" males are about 3 cm long, and the females up to 4 cm. Adding to the intimidation factor is the behavior of the males, which gather in "leks" of up to 70 individuals -- all buzzing around and defending small territories, awaiting the appearance of virgin females to mate with. We are lucky enough to have an annual colony of cicada killers right against our building at work, and it is unsettling to stand in the midst of these busy insects even for the knowledgeable among us. I've had plenty land on me as I sat in the middle of the lek, and I still get creeped out when they settle on my back where I can't see them. Cicada killers are truly frightening to folks who don't know what they are, but rest assured for all their size and hectic activity, they are wussies.

Males -- the most conspicuous -- cannot sting. Females can sting, but must be strongly provoked (or stepped on). Even so, as members of the wasp family Crabronidae, they have weak stings that, unless you are allergic, would feel like a pin prick and diminish within an hour.

It is high time for cicada killers now. They emerge in coincidence with cicadas, having overwintered underground, first as larvae in cocoons, then as a spring-developing pupae. Males emerge first, a week or so ahead of females. Unlike many insects, a female cicada killer will only mate once. Presumably once mated the females give off some scent that males detect when close by. I've seen males approach, knock over, or tackle females, but immediately fly off rather than try to mount them. Virgins, on the other hand, may find themselves in the midst of a determined, enthusiastic ball of males, one of which will win her over.

Once mated, females find an appropriate area, often a well-drained slope near a woodlot, and build a burrow up to three feet deep (not a typo). Our colony is in a border of fist-sized rocks on top of sandy soil next to a sidewalk. Burrows may have several branching nest chambers. In each, the female will place one or two paralyzed but living cicadas on which she will lay her eggs. Eggs are always laid under one of the second legs of the cicada, apparently the best spot for a little wasp larva to start eating.

The female cicada killer decides the sex of her offspring, because she stores sperm in a structure called a spermatheca, and uses the sperm to fertilize her eggs as she chooses. She will lay an unfertilized egg on a single cicada for a male, and a fertilized egg for a female; the fertilized eggs also get a second cicada. Since it is the females that have to hunt and carry around cicadas (which are much heavier than the wasp), they are bigger than males and need the extra provisions. Each female cicada killer will lay about a hundred eggs in a season, most of which will be males.

Even among males, there is size variation, depending on the size and condition of the cicada they were provided with as a larva. Paralyzed cicadas usually remain "fresh," but the situation is complicated by rivalry for the cicada itself. Certain species of fly wait at the entrance of the cicada killer's burrow in order to lay their own eggs on the paralyzed cicada. In this case, the fly larvae compete for the food source.

In less than three weeks after they emerge, males die. The females live four to five weeks, giving them time to construct and provision their nest burrows. Underfoot, cicada killer larvae slowly consume their rations. It will be another year before a new generation appears, intriguing some of us, and fooling others to fear them.

---

Many thanks to Prof. Chuck Holliday's Cicada Killer Page, a one-stop source for all kinds of life history and research data on these fascinating insects. 

Please don't molest a colony of cicada killers. If you need to know more about why they are harmless and why dousing them with a load of pesticides is ineffective in the long run, check out Joe Coelho's web site; he's a colleague of Holliday.

Top photo: Male cicada killer, on the lookout.
Center: Potential hapless victim, a Swamp Cicada (Tibicen chloromera).
Bottom: Female cicada and co-worker's hiking boot.