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Field Journal May 16-31

Thursday, June 1, 2017 @ 05:06 PM
posted by veronica

By Sibylla Brown, Timberhill Oak Savanna

Beginning May 16 we had nine straight days of rain.  This was followed by a cold front which dropped daytime temperatures into the sixties and nighttime temperatures into the forties.  Not very favorable for observing butterflies but it certainly stimulated the plants.  Phlox pilosa filled a small West 40 prairie remnant with its bright pink bloom. Purple Twayblade orchids which are scattered throughout our restored savanna are also blooming.  Leadplant is so abundant in the East Savanna that it’s hard to keep from stepping on it.   

And in the southeast woodland Yellow Lady’s Slipper orchids are blooming. I usually check them by May 1 and cover them before the deer eat the blossoms.  This year I didn’t do it soon enough.  When I checked them on May 19 the deer had already eaten four of the flower stalks.

Yellow Lady’s Slipper

Milkweeds, dogwood, and dogbane, all excellent butterfly nectar sources, are in bud and will soon be open.  Purple Milkweed is more abundant than usual.  East of the driveway, for example, where I usually find two or three plants I counted fourteen.  In the West 40 savanna there are twice as many as last year.  I am also finding it in places I’ve never seen it including under dense canopy. 

Despite the unfavorable weather I did have a notable butterfly sighting — a Zabulon Skipper in the West 40. This rare breeding resident is strongly habitat dependent.  Peck’s Skipper,  Common Sooty-wing and Silver Spotted Skipper (very abundant) were also on wing during our sunny spells.   Once the weather warmed up Tiger and Giant swallowtails, and Red-spotted Purple became common sights. 

Zabulon Skipper

The first saturniids, wild silk moths, of the season came to our moth collecting black light on May 26. That night I collected a Rosy Maple Moth.  This is the first time I’ve seen this species at Timberhill.  I was surprised not to have seen it before since the larvae feed on silver maple which is abundant along our creek bottoms.  Two other silk moths, a Luna and an Io moth came to the light the next night. With its prominent hind wing eyespots Io Moth is one of the most recognizable moths.  Although it maintains huge populations in some U.S. locations Iowa must now be on the periphery of its range.  Since 2010 there have only been nine recorded sightings in Iowa. 

On May 28 we also observed a Hermit and Twin-spotted Sphinx moth at our black light. 

Summer mushroom season began with a dense fruiting of Oyster Mushrooms around the base of a dead elm.  Instead of the usual white, these specimens were pale yellow.  Because of the cold weather?   In the south meadow we had a heavy fruiting of Agaricus arvensis, Horse Mushroom.  Regarded as one of the most delicious edible fungi this is the first time we have seen it at Timberhill.     

I know that summer is almost here when I wake up to the Whip-poor-will’s call.  Although I’ve never seen one, I hear its song just before dawn every morning and each night as I’m falling asleep.  That certainly beats using an alarm clock.     

Insects of Iowa website lists Iowa moth and butterfly records:  http://www.insectsofiowa.org

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