Archive for the ‘Julie Craves’ Category

Jumping Oak Galls


Wednesday, December 19th, 2012
Jumping Oak Galls

Jumping Oak Galls © Julie Craves

Jumping Oak Galls by Julie Craves

A move to a new house has been responsible for my lack of productivity here the last few months. Now that we are settled in, we are anxious to get to know our large property. We have eight acres of wet woods, and while my bark identification skills are serviceable, I’ve been spending more time looking down at the ground to unlock some of the secrets of the forest we will now stewards.

Many of the mature trees are Black Cherry, Bur Oak, and Swamp White Oak. I noticed that many of the fallen oak leaves were pocked with dozens, if not hundreds, of round lesions, each the size of a pinhead. On the uppersides of the leaves, they looked just like pimples. On the underside, each lesion was a shallow pit that was either empty or had a tiny nodule nestled in it.

Those nodules are galls, created by very minute wasps in the genus Neurotarus. They’re known as jumping oak galls, because when the galls detach from the leaf and fall to the ground, the wasp larva inside will sometimes wiggle around and cause the gall to move. The fully developed wasp larvae will overwinter in their galls on the ground. Galls that remain on the leaves are probably doomed – they’ll either dry up and die, will expire because they have been parasitized or their galls have been invaded by insect inquilines, interlopers that feed on the gall tissue.

If all goes well, these galls will produce the all-female generation. Neurotarus wasps, like many of the others in their family, have elaborate life cycles that include alternating asexual and sexual generations.

Members of this family of wasps are quite host-specific, usually attacking only one or a few species of oaks; none use hosts in both the red and white oak groups. All the gall-bearing leaves I found were white oaks, with none on the plentiful red oaks present on the upland parts of the property.

A Cabbage by Any Other Name (Would Still Stink)


Tuesday, December 11th, 2012
Skunk Cabbage

Skunk Cabbage © Michael M. Smith/View Two Plus

A Cabbage by Any Other Name (Would Still Stink) by Julie Craves

The edge of the wet woods on our property marks the border of an extensive plot of Skunk Cabbage (Symplocarpus foetidus). If you’re out and about in late winter in a forested area with perpetually mucky soil, you are probably familiar with this unusual plant. Their large, mottled, maroon, hooded spathes cradle the inflorescence, and show themselves through the snow like the caps of crouching sylvan gnomes. When the small flowers bloom, they stink like carrion to attract the earliest pollinators on the wing, mostly small flies and gnats. These not only find the stench appealing, but are also attracted to the heat generated by the flower spike. The warmth is thought to protect the flowers from freezing, provide a warm micro-environment for pollinators, and aids in broadcasting the floral odor by taking advantage of the spiral construction of the spathe and thermal air currents.

After the spathe withers, the very large leaves unfurl from a patient neighboring shoot. The dramatic leaves might be over two feet long, but die off by mid-summer, melting into the wetland as they decompose. A number of fly larvae have been found to feed on rotting Skunk Cabbage vegetation.

Skunk Cabbage

Skunk Cabbage © Rob & Ann Simpson

Fewer of us are likely to see the fruiting bodies – not only is Skunk Cabbage habitat likely to be mosquito-infested and squishy in summer, but the fruits themselves tend to be hard to spot. They look like solitary hand grenades, or maybe small stalked pineapples, mired in the mud. They’ll soon fall apart, with the seeds falling on the wet ground. The fibrous roots of young Skunk Cabbages are often exposed in humps on the soil surface, and reflect the shallow germination. As the perennial plants age, the roots become deeper and voluminous, anchoring plants and pulling them deeper and deeper into the earth.

Still later in the season, when insects have died and the ground is starting to freeze, you might come across the tips of new leaf spikes poking through the leaf litter, gaining a head-start on the next growing season. As steward of such a large colony, I look forward to seeing these fascinating plants rise from the snow next year.

Spots of Tar


Wednesday, December 5th, 2012

Silver Maple Tar Spots © Julie Craves

Spots of Tar  by Julie Craves

In the upland area of our new property, oaks and cherries give way to maples. Judging from the fallen leaves, most are Silver Maples. In my search for other species, I noticed that many of the fallen maples leaves were disfigured by black blobs. I had noticed a more severe outbreak these spots on maple leaves still on the trees at my urban field site earlier in the year. These distinctive spots are caused by fungi in the genus Rhytisma, commonly (and appropriately) called tar spot disease.

The fungi overwinter in the spots, which are known as stromata, on fallen leaves especially if they are in a damp, protected location. Spores burst forth from the spots in the spring, coinciding with new leaf emergence on nearby maple trees. The wind-dispersed spores can then infect new leaves. Infections begin as yellow spots that eventually evolve into the tar-like blobs we see in autumn.

Generally, tar spot doesn’t do much harm other than cosmetic, even though in the last several years many maples have had dramatic infestations in the upper Midwest. A particular species of Rhytisma infects Silver Maples, while another, non-native species that favors introduced Norway Maples has been increasing in the northeastern U.S. the last decade or so. This explains the sparsely-blotched Silver Maple leaves on my property versus the heavily-splotched Norway Maples at my urban field site; the fungus that infects the latter tends to create more spots that congeal into large patches.

It has been speculated that tar spot on Norway Maples is on the rise because of cleaner air quality (the fungi are thought to be sensitive to pollution). And recent research has shown that leaves infected with tar spot decay more slowly than uninfected leaves, which may indicate that there is a more subtle effect of this disease on nutrient cycling or soil conditions. These are interesting interactions and synergies to study, especially given the ubiquity of Norway Maples in urban areas, where soils are subject to so much alteration already.




Tree Frog in the Bathroom


Tuesday, November 27th, 2012
Cope's Gray Treefrog and Common Gray Treefrog

Cope’s Gray Treefrog and Common Gray Treefrog © David Liebman

Tree Frog in the Bathroom by Julie Craves

The first amphibian we found at our new property was a gray treefrog. We have a wooded wetland, but we found the frog on the floor of an interior, windowless bathroom on our second walk-through prior to buying the house. Presumably it gained entry through the exhaust fan. I suppose this would have been a turn-off to some prospective buyers, who might wonder what else could make its way into the crapper from outdoors, but it charmed us. My husband scooped up the little hopper and placed it outside where it belonged.

We’ve since seen and heard many of this frog’s kin and neighbors. In the eastern U.S., Hyla versicolor and Hyla chrysoscelis are the two sister species of gray treefrog, Eastern and Cope’s. The former has a slower call than the latter, which is the best way to tell these two apart, unless you have your heart set on counting chromosomes.

Cope's Gray Treefrog and Common Gray Treefrog

Cope’s Gray Treefrog and Common Gray Treefrog © Bill Beatty

My ear has not yet heard enough of both species to be able to distinguish the pace of the bird-like trills. Some studies have suggested that Cope’s Gray Treefrogs can tolerate (or prefer) lower humidity, more often call from trees, and consequently eat more arboreal insects, while Eastern Gray Treefrogs like it more humid, tend to call closer to the ground, and eat more terrestrial insects. Even at the end of a dry, hot summer, treefrogs were pretty ubiquitous high and low around the property. Perhaps we have both species, although confirmation will prove difficult.

But no matter. These are my favorite frogs, so beautiful in mottled, slightly warty patterns of green, gray, and brown. They are especially hard to spot when perched on tree bark, but stick out like a sore thumb when adhered by sticky toe pads to porch lights, window screens, sliding glass doors…or bathroom floors.

True Shrews


Friday, August 17th, 2012
Cinereous Shrew

Cinereous Shrew © James F. Parnell

True Shrews by Julie Craves

Despite their abundance, shrews are seldom seen – alive, anyway. Largely nocturnal, shrews have supercharged metabolisms, with heart rates of 800 to 1,000 beats per minute. When I have found dead shrews, they have usually been intact and uninjured (occasionally even warm), as if they just burned themselves out.

The common shrew in my area is the Masked Shrew (Sorex cinereus). It may well be in your area as well, as it is widely distributed across North America.  They are found in a variety of habitats, but usually close to water. In fact, moisture seems to be a key variable in Masked Shrew numbers. There tends to be little reproduction in drought years due to a reduction in favored prey items: leaf-litter invertebrates such as worms and insect larvae.

Although I have had more instances of encountering dead shrews, I have seen many more individuals alive. This is because three times in my field career, I have stood amidst a “shrew party.” This has always happened early on a spring morning, while I am moving slowly along trails doing a bird survey. Each time, I noticed persistent rustling in the leaf litter. Looking down, I’d see a shrew darting from a fallen log to a tangle of vines. Then another, scooting over and under dried leaves. Sometimes, one would race across my boot. Very high-pitched squeaks accompanied the speedy, vigorous, seemingly-joyful coming-and-going of four to fifteen shrews, all in an area of a few square feet. It lasted only a few minutes, then the forest floor would fall silent.

Masked Shrews are rather notoriously averse to company. Shrew aggregations like these are thought to be mating parties, but little is known about the behavior, or the rest of their social habits.

In my mind, a lifeless shrew is the antithesis of what shrews are all about. On the glum occasions when I find a dead shrew, I draw upon my experiences amid spirited, lively shrews. That is the true essence of a shrew.

My Dirt is your Disguise – Insects


Friday, August 10th, 2012

My Dirt is your Disguise – Insects by Julie Craves

Okay, so domestic chores are not one of my strong points. Yet it was alarming to see a dirty bit of crud in the foyer begin to move under its own power across the entryway. Had I neglected housecleaning for so long that dust bunnies were becoming living organisms, like some Far Side cartoon?

A closer look revealed the animated detritus was an immature Masked Hunter (Reduvius personatus), a true bug inadvertently introduced from Europe sometime before 1900. They are now found over much of the U.S., most frequently being found in the central and northeastern states. They prefer dry conditions, so they are often found indoors. We have found them near doorways and on the front porch, where they hang out to feed on the insects attracted to the lights.

As do other members of the genus, the immature stages of the Masked Hunter look like smaller versions of the adults, except they are covered with fine hair-like structures which collect dust, dirt, and lint (adults are sleek and black). This camouflage perhaps helps the youngsters sneak up on their prey.

Like other assassin bugs, Masked Hunters stab their insect prey with beak-like mouth parts, then inject chemicals that both subdue the victim and liquefy their innards for easy slurping. While small – under an inch – Masked Hunters can nonetheless inflict a painful poke to humans if they are mishandled. They’re benign, though, and don’t transmit any diseases. In fact, they are often considered pretty good housemates. Masked Hunters are mainly nocturnal, and bed bugs are a favorite food, accounting for their alternative name “masked bed bug hunter.”

Bed Bugs Insects

Bed Bug © Will Ferguson

I’m happy to report we don’t have bed bugs, and I’m okay with allowing these little predators to keep the foyer and porch free of other insect invaders. Since covering themselves with debris only improves their hunting prowess, I’ve decided to put off the dusting for just a little while longer…

Invader, Meet Invader


Friday, August 3rd, 2012

Invader, Meet Invader – Garlic Mustard by Julie Craves

The non-native, invasive plant Garlic Mustard (Alliaria petiolata), is such an abundant part of my urban landscape that I often don’t even notice it. So I surprised myself one day walking through my field site because, although my thoughts were elsewhere, I stopped in my tracks when I saw a Garlic Mustard plant with chewed leaves. Part of the success of many invasive, non-native plants is that they flourish in regions where they have no natural enemies. Not much eats Garlic Mustard in North America. Apparently I was so used to seeing intact leaves that these obviously browsed ones triggered a response in my subconscious.

Garlic Mustard Wildflowers

Garlic Mustard © K. P. McFarland

When I stopped to take a look, I saw two small Cabbage White (Pieris rapae) butterfly larvae feeding on the leaves. That’s another non-native, widespread species that’s so ubiquitous I hardly register their ever-presence. I found two more Garlic Mustard plants nearby that each had a Cabbage White caterpillar feeding on it.

Here, the plot thickens.

Cabbage White larvae feed on many species of plants in the mustard family (Brassicaceae). This includes crop species introduced into North America, including Brassica oleracea (from which cabbage, broccoli, kale, and other vegetables are derived), mustard greens, and turnips. In Europe, Cabbage Whites also use Garlic Mustard as a host plant.

Cabbage White Butterflies

Cabbage White © Rick Cech

Both Cabbage Whites and Garlic Mustard were first recorded in North America in the mid-1800s, in Quebec and New York, respectively. Despite long association in both their native and introduced ranges, there are relatively few reports of Cabbage Whites using Garlic Mustard as a host plant in North America.

Studies have suggested this may be due to the fact that the butterflies have so many delicious choices of host plants here that they can choose those that they prefer (mustard greens are a favorite), and don’t need to resort to Garlic Mustard. There is an organic garden and lots of “preferred” choices within 100 yards of where I found these caterpillars. Why Garlic Mustard was chosen instead in this case is a mystery.

I brought the four Cabbage White caterpillars indoors and successfully raised them to adulthood on wild Garlic Mustard. I released the adults, hoping that perhaps they might go on to begin a population with a taste for a host from the homeland that wasn’t also destined for own our dinner plates.

House of Frass – Insects


Friday, July 27th, 2012

House of Frass – Insects by Julie Craves

We are long overdue in painting the exterior of our house. Not only would we like to sell it in the next year or two, but of course we feel how our house looks reflects upon us. And “shabby,” “peeling,” and “fading” are not how we like to describe ourselves.

Things could be worse. Let’s say we were the larvae of one of the Cryptocephalinae, or case-bearing leaf beetles. Our “home” (the case) would be made from our own excrement. We all know the longer we live in a house, the more crap we accumulate. In the case of these beetle larvae, this true in a very literal sense. Toting around an abode made of your own turds is a good way to be unobtrusive to predators while in a vulnerable state – or completely unappealing if discovered. In many species, the adult beetles are quite attractive, reward for spending the beginning of their lives covered in their own waste.

Canada Thistle Wildflowers

Canada Thistle © Ron Austing

Some members of another subfamily of leaf beetles follow a similar lifestyle, such as the tortoise beetles. These insects don’t construct quite as solid a structure, but nonetheless do create external self-protection. We recently came across some Thistle Tortiose Beetles (Cassida rubiginosa) on Canada Thistle (Cirsium arvense); neither species is native to North America. Most of the beetle larvae were festooned with frass (the official term for insect poop). Some were not, and looked like spiny trilobites. Either way, creepy.

Green Lacewings Insects

Green Lacewings © Edward S. Ross

The larvae of insects in a completely different family, the Green Lacewings (Chrysopidae) also have spiny exteriors and decorate themselves with debris. These predatory larvae are a bit more catholic in their use of materials. There may be some frass, but usually they use bits of plants and body parts of recent victims. In any event, all of these mobile homes serve as disguise or protection or both.

Many insects utilize convenient substances in the creation of temporary housing. These are just a few examples of the ones that are making do by making doo.

Maple and Cocoa


Tuesday, July 10th, 2012

Kent’s post awhile back on the stinky-sweet smell of the Roundneck Sexton Beetle brought to my mind some birds I have smelled. Actually, I’ve smelled many thousands of birds…it’s hard not to with my nose just centimeters away as I check fat levels and extent of skull ossification during the bird banding process. Most birds don’t really have much of an odor, but there have been some notable exceptions.

American Goldfinch adult male, breeding © Rick and Nora Bowers/VIREO

I have banded far more American Goldfinches in fall and winter than in spring, but recall one April when each goldfinch that came through my banding lab smelled faintly of maple syrup. We decided that the finches were probably feeding on maple leaf buds or perhaps even a little sap – generously provided at the wells of Yellow-bellied Sapsuckers.  I’m not sure this satisfactorily explains it, since maple sap doesn’t really have much odor, although I cannot verify exactly what crushed maple leaf buds might smell like.

Yellow-bellied Sapsucker, adult female © Garth McElroy/VIREO

Still, that carries some logic. Seemingly defying explanation is why quite a few White-crowned Sparrows, over a number of years, have smelled like suntan lotion. Maybe cocoa butter is more precise, but I will have to say it was so distinctly like the old Coppertone lotion that the first time I got a whiff I was immediately transported back to my childhood. That first time, I accused the bander who had handled the bird just before me of having lotion on their hands – a no-no in my lab. The bander was innocent, and the aromatic sparrow got sniffed by everyone. We all agreed it smelled like suntan lotion.

This started the Rouge River Bird Observatory tradition of bird sniffing. We’ve found a number of other cocoa-buttery White-crowned Sparrows, as well as a few birds here and there that smelled kind of interesting, in non-descript sorts of ways. There are a few species whose odor – or lack thereof — will remain unexplored. There’s no way I’m going to go for close whiffs of Rose-breasted Grosbeaks or Cooper’s Hawks

The Moth that Came from the River


Wednesday, June 20th, 2012

Chestnut-marked Pondweed Moth by Julie Craves

One of a child’s first natural history lessons is usually that caterpillars grow up to become butterflies or moths. Eager to witness this transformation, we seek out caterpillars in yard and field to shepard through this remarkable metamorphosis. We soon learn the importance of raising the larvae on the same species of plant on which they were found. For many of us, this is our introduction into the interdependence of plants and animals, and the complex life cycles of even common organisms around us.

A couple of years ago I was doing an insect survey on a property along the Detroit River. I noted a pretty little moth which was quite common; many appeared freshly emerged, which made me curious about what the caterpillars fed on. From my photograph (above) I identified the moth as a Chestnut-marked Pondweed Moth. “Pondweed” is a pretty generic term, but I’ve generally heard it refer to submerged plants in the genus Potamogeton. Sure enough, Potamogeton is the host plant for this species…and the larvae are aquatic. I consider myself pretty well-versed in various butterfly and moth species and their host plants, but aquatic caterpillars were new to me.

This moth is not unique. In this same genus are species whose larvae feed on waterlilies, watermilfoil, and other water plants. Most feed on submerged parts. Other moths in the same family feed on algae scraped from rocks or diatoms trapped in silken sheets spun by the caterpillar. Many have gills for all or part of their larval stage. Females of some species may submerge themselves in an air pocket to lay eggs up to four meters underwater! Members of a number of other moth families are also known to have aquatic larvae.

When I think of flying insects that have an aquatic larval stage, my first thought is always dragonflies. Then many species of flies, as well as beetles, caddisflies, and some true bugs. Now I can add moths to this list, something I never imagined when I raised my first sphinx moth from a “tomato worm” as a bright-eyed child.