Skull Identification

I received a plastic bag with a "gift," a skull with a request for identification.  Some one else might have considered this a threat or at best a bad joke.  Amy Short knew this would be welcomed, a find from her mother's yard.  There were no other clues to its identity, no lower jaw and only one residual tooth.  It had been chewed by other animals in need of calcium.  I was tempted to send it off for an expert opinion from Richard Herman, our local skull guru but decided to take a swing at it.  I got lucky because of several unique features.

It was obviously a herbivore with the absence of canine teeth and the large gap between the incisors and the molars.*  The canine tooth canal was long, 1.5" on a curve suggesting that it was not only a rodent, but one that used its teeth hard enough to require rapid growth.  While the rodentia family is large, including beaver, mice, rats and rabbits, the skull length of 3.5" eliminated a lot of these.

Looking over the choices in Wild Mammals of Missouri (Schwartz) I came across the perfect fit.**  This skull belonged to a woodchuck, a.k.a. groundhog, Marmota monax.  I have been trying to trap the ones that are undermining our century old barn without luck for 3 years, and here was the skull, the ultimate irony.

The key was the length of the skull, but first the rodent identification.  This site from Cornell.edu gives the basic features identifying it as an herbivore by the absent canines and large gap between the incisors and molars.  The long incisor roots suggested unremittingly growing incisors, a characteristic of the Order Rodentia.


Once identified as a rodent in Missouri, the skull length narrowed the field.  It wasn't rounded like a beaver, too large for a rabbit and only a few species are left.  To quote Wild Mammals of Missouri,  "It is easily distinguished from other skulls...by the following characteristics:"

• Large size
• Flat skull when seen in profile
• Postorbital processes projecting at right angles to the length of the skull
• Depressed area between the postorbital processes 
• Prominent auditory bullae indicating hearing acuity.

 *For the basics of identifying carnivore, herbivore and omnivore, go to Cornell.edu.

**  Animal Skulls by Mark Elbroch is the ultimate source, very detailed with lots of keys.  Wild Mammals however is a great local resource and has dental guides and measurements that works for almost all of our Missouri skulls.

Pawpaw Flowers

Pawpaw flowers in full bloom - REK

This is the time of year we start monitoring the pawpaw flowers.  Sudden freezes turn them into shriveled dark brown blobs, robbing them of the chance to make fruit.  It is a miracle that we ever have any pawpaw trees, let alone fruit.  Their fruits are popular with squirrels, raccoons, and bears.  In season we see bear scat filled with seeds, the pawpaws' transportation out of the neighborhood.  Since their fruit are challenged by late frost, this method of propagation is hazardous.

Pawpaw flowers, fresh, dead and frost damaged - REK

Pawpaw, (Asimina triloba) have several survival techniques.  Their main method is to reproduce by suckers, roots extending out to establish trees nearby in an expanding community.  Left alone they could cover a large area but as a forest matures over years around them, their expansion is controlled.

Like other species producing dark brown to purple flowers, they rely on a smell of rotting flesh to attract pollinators, not butterflies but flies and other species attracted to the odor of death.*  Their flowers meanwhile are pollinated in a hit and miss fashion by flies, beetles and other species.  In some limited attempts to grow pawpaw commercially, growers actually hang dead fish and other lures to attract these morbid pollinators to their trees.

Bud ready to flower

We have noticed over the years that the flower blossoms develop and open up sequentially over 4-6 weeks in the spring.  Currently we have dried shriveled flowers killed by frost 3 weeks ago as well as recently stunted blossoms from the freeze a few days ago.  On the same tree are unopened buds both ready to open next to tiny emerging flower buds, the whole spectrum on a single tree.

Fresh flower and small new flower bud - REK

The early blooming pawpaw has thus found a way with dealing with these setbacks by spreading its flower buds over more than a month.  While observing this budding over time, we haven't noticed whether it ends when the frosts stop.  It is possible that this continuing flower bud propagation is the plant's response to frost damage.

*Further information on Pawpaw odors is in this paper.
Previous pawpaw blogs have covered Zebra Swallowtail eggs, the  butterfly's premature delivery and the Asimina webworm moth that lives curled up in pawpaw leaves.

Dusky Skippers Puddliing

Puddling party in the valley - REK

Juvenal's Duskywing - REK

We are seeing lots of Duskwing Skippers the last week, clustered in groups of 50-100 plus gathered on dry sand in our gravel drives.  These are the Rodney Dangerfields of the butterfly world and some would even go so far as to separate them from butterflies altogether.  The duskywing skippers are notoriously hard to identify by species and only the fact that I was seeing such large numbers at scattered sites made me curious enough to the trouble to ID them.

 These are all Juvenal's Duskywings, Erynnis juvenalis.  They  are nearly identical to
 Horace's Duskywings and both were named for Roman poets for unknown reasons.  The marking details separating the two species are very minute, one requiring pulling the forewing forward to expose two tiny white apical spots, cumbersome for me and I suspect embarrassing for the butterfly.  From now on I will confidently call them Dusky Skippers and skip on to the next species.

Juvenal's Duskywings fly earlier in the year than Horace's.    Juvenal's was one of the first North American butterflies to be described.  They were initially associated with dry, sandy regions with shrub oak but are found anywhere in the eastern US where their caterpillar host plant oaks occur.  Oaks occur all over our land so they have a lot to choose from.

E. juvenalis caterpillar -  Bob Barber CC

Males will cling to branches along the edge of woodlands and patrol for females.  Eggs are laid on early oak leaaf buds or seedlings where their caterpillars will  feed on leaves and rest in nests of rolled or tied leaves.

  Tom Murray

 Puddling or mud-puddling behavior is observed in lepidoptera and a few other insect species.  It is a way for them to collect minerals such as salt similar to what sweat bees do landing on our skin in summer.  Some species will do this on animal dung, presumably collecting ammonium.  These gatherings are predominately male as they collect sodium and amino acids which they then transfer to the female as a "nuptial gift" delivered with their spermatophore during mating.  It is common to see several species puddling together in the summer.


When I began writing this I suddenly noticed something else about the puddling photograph.   While the Duskywings wingspan measured less that 1.5" there was something even smaller on the sand.  See if you can spot them in the picture at the top.

 

There are two tiny black moths with multiple white spots on their wings.  These are Mournful Thyris, Thyris sepulchralis with a wingspan of less than an inch.  While most moths are out at night, these are day flying moths that feed on flower nectar and are noted for collecting fluid on moist sand.  Our sand appeared dry to sight and touch but many species shoot fluid out their rectum to moisten the area and dissolve the salts for absorption.  (Note to self - wash hands after testing sand).

One photographic trick is to pour a little salt water on the ground and wait for butterflies to puddle for the camera.  Some photographers suggest placing a decoy of a dead butterfly or even a piece of colored paper to attract species in the neighborhood.  A naturalist, most likely but not necessarily male, may chose to supply ammonium in the form of urea from a convenient resource. 

Find the moths?  Click on this picture.

Abbot's Sphinx Moth

Abbot's Sphinx Moth on the screen, its abdominal tip in its characteristic upright position - REK

I was closing the window one early morning at Bull Creek when I saw a dry leaf stuck to the inside screen that hadn't been there the night before.  It turned out to be a very cold Abbott's Sphinx Moth, Sphecodina abbottii.  How it managed to pupate and emerge as an adult in the house is beyond me.  Their usual time is May to June in most of its range and the males are reported to fly around dusk, the females flying near midnight.

Note glimpse of the yellow patch on the covered hind wing - Jon Rapp

Peterson's guide describes it as having deeply scalloped outer wing margins with swirling black lines.  It has a bright yellow patch on the basal hind wing that doesn't show in pictures with the wings folded at rest.  The abdomen ends in an unusual 3-pronged tip that it holds upright.  I tried to photograph it later in the day but the overcast sky dulled its colors so I turned to Jon Rapp as usual.

 First instar - Jo Ann Poe-McGavin 

 Last instar -  Jo Ann Poe-McGavin

The larvae feed on grape species, Vitis and Ampelopsisare.  They are equally cool looking, going through dramatic changes with each molting.  As described in Bugguide:

Knob as an "eye" - REK

"Larvae start out green with a horn on the final segment. Middle instar larvae are whitish to blue-green with dark faint cross-stripes and the horn replaced by an orange raised knob on the last segment (A8). The last instars may be either brown with a "wood-grain" pattern or brown with ten pale green saddles along the back. In these late instars the knob resembles an eye."

Note the 3-pronged furry abdominal tip held upright - REK

I kept my specimen in the refrigerator to get a better sunlit picture of the antennae.  It is described as flying with a buzzing noise, resembling a bee with its flashes of yellow.  Holding it, I could feel the buzzing as it warmed up its flight muscles, its oval body impossible to grip until it made its buzzing escape into the wild.  A much better fate than clinging to our screen, looking longingly at freedom.

Released, just before flying off - REK

 Addendum:
Not to be out done, Kevin Firth sent me his gorgeous picture of a new (to us) moth he photographed at Rocky Barrens CA recently.  This is likely Kent's Geometer, Selenia ketaria.

Smooth Rockcress

Smooth Rockcress - Mark Bower

We celebrate the arrival of spring in many ways - the arrival of Harbinger of Spring, the first butterfly, the first show of redbuds.  Then small white flowers appear on the serviceberry, the preview of the main act, the flowering of our Missouri State Tree, the dogwood.

"Our" Smooth Rockcress - REK

Spring comes on in much smaller acts as well, discovered before most plants and shrubs cover them up with leaves.  We found rather inconspicuous dark green leaves of Smooth Rockcress, Boechera laevigata, on a moist rock seep along the base of a bluff, nurtured by a dense mat of moss.  The tiny gaping jaws of leaves on the right exposed flower buds, waiting to make their appearance in a month or so.  In the shade of the rocks I couldn't photograph the buds but the next day Mark Bower sent me a beautiful set of pictures of Smooth Rockcress that he had found.

B. laevigata is a biennial, meaning that it has a two year life cycle similar to thistle, teasel and garlic mustard.  The first year its energy goes into growing vegetative structure, its roots, leaves and very little stem, staying close to the ground.  The second year the stem "bolts," the stalk shooting up where it flowers and produces seeds.

Rockcress buds patiently waiting - Mark Bower

Growing on moss covered rock - Mark Bower

Even tiny plants have their faunal associations.  The tiny flowers are pollinated by equally tiny bees including Andrena arabis (Rock Cress Andrenid Bee).  The leaves are hosts to the beautiful Falcate Orangetip butterflies we have been seeing the last few weeks.  They will be laying their eggs and then dying off as their caterpillars develop over several weeks, then form a chrysalis in May that they will survive in until next spring.  Although this sounds like a risky lifestyle, it obviously works for them.

from Minnesota Wildflowers

We will be monitoring the little rockcress during the late spring when it will typically bloom.  The flowers last for 1-2 months but are hard to see, the white petals barely extend beyond the green sepals, all less than a third of an inch long.  We have flagged the area to be sure to find them.

* The life of the Orangetip Falcate is the subject of this 2015 blog.

Nibbled down- Mark Bower

Addendum:  Mark was following the plant to get a picture of its flowers, but a herbivore beat him to it overnight.  There isn't a lot to eat right now on the hillside so it is understandable.  Squirrels are reduced to crawling out on branch tips to nibble on tree buds while dangling precariously.  This plant lost its chance to procreate so I will have to guard ours carefully.

"This Buds for me  -  REK."  - 

Luna in March

I was out checking on our bluebird boxes and nearly stepped on something pale green in the mixture of dormant and new green grass.  It was a Luna Moth (Actias luna) desperately clinging onto a few grass blades 7" tall.  It was whipping around in the wind said to be 12mph with gusts to 20 although it must have felt like more.  In the picture below you can see it being lifted by a gust.

Hanging on but almost airborne in the gusting wind

 Male with large feathery antennae -  Bugunderglass.com

Female antennae - REK

Although everything else is appearing early this spring, I was still startled to see it.  This was a female as evidenced by the smaller antennae.  Males have large plumose (feathery) antennae, "My what large antennae you have.....The better to sense your pheromones, my dear."

The subject on antennae and pheromones alone is worth a book.  An insect may rely on a hundred different pheromones during their lifetime according to Thomas Eisner, the "Father of Chemical Ecology."  Those hair-like structures on the antennae are olfactory organs.  There may be up to 60,000 on a single individual in some species.  They are capable of sensing a single pheromone molecule from over a mile away.  And there might be only one molecule in a cubic yard of air.

In the case of Luna and other silk moths, time is of the essence.  Luna moths do not eat and don't even have an intestinal system.  With a life span of a week, quick mating and egg laying is crucial.  Mating occurs usually within 24 hours of emergence from the pupa which usually occurs in the morning.  The wings are initially shriveled and expand by hanging them down as body fluid is pumped into the vein-like vessels.  They then hang on while the wings dry over 2 hours to hold their shape.  In the picture below you can see that the long trailing "tails" of the wings were twisted by the heavy winds and have dried in a spiral..

Deformed tails of the wings, whipped by the wind.

I sent the photographs to Chris Barnhart who responded that evening.  "It's a girl! Get eggs if u can".  I was embarrassed that I hadn't thought of it earlier.  Guilt ridden, I went back out at 10PM  and searched the area with a flashlight and the truck headlights, but she was gone, likely having been blown of her grass stems.

The Other Mockingbird

Barb called me outside yesterday morning to hear the mockingbird calling.  I went back for the camera and managed to get a picture of the bird when it dropped down to the ground.  When I saw it was a brown thrasher I was momentarily disappointed.  Then Barb did a quick search and found that it was the "mockingbird" we heard.

According to Allaboutbirds, the Brown Thrasher has one of the largest repertoires of any North American songbird, up to 1,100 song types.  Ours was playing its greatest hits but kept coming back to its version of the whip-poor-will, a nocturnal bird that has kept us awake during its breeding season. The other key to identifying the call was its repeating the song twice, then immediately starting the next tune while a mockingbird tends to repeat it three times.

The Brown Thrasher is rather distinctive with its long, slightly curved beak, long tail and a bright yellow eye that is prominent.  They migrate up this time of year, extending all the way to Canada.  There are reports of individual birds reaching Germany and England once each, probably on a foreign vacation.  Lisa Berger came up with more range data:  "

"They are listed as an uncommon Southern Missouri winter resident.  Locally, we see them on Christmas Bird Counts, similar to E. Phoebe.  These guys are more common in winter than my perception simply because they aren’t singing!"

They feed on the ground as well as gleaning fruit and berries in season.  Currently they are working our lawn, sweeping it with their long beaks looking for any available insects.  Then they fly up into the trees or wires to announce their presence, call for a mate, or just sing because it is a beautiful morning.  I went out to listen again this morning and was rewarded with a bird singing on the wire.  While our great sonic "discovery" didn't advance ornithological science, it made our day a little brighter.