Butterflies

by Carl Strang

Butterflies are the most conspicuous insects, and to the extent that they are representative, they are telling us that insects got through the winter in pretty good shape. Butterflies have been abundant and diverse this spring, both species that wintered here and ones that have migrated north. Earlier I mentioned red admirals in this context, and their congeners the American lady and painted lady butterflies have been showing up as likely migrants as well. A member of a species new to my experience appeared at Mayslake Forest Preserve last Thursday.

Obviously a fritillary, it seemed too big for a meadow fritillary and too small for other species of my acquaintance. Also, it lacked silvery spots beneath the hind wing.

My practice is to photograph doubtful cases when I can, and this time it paid off. The newcomer is a southern species known frequently to wander north, the variegated fritillary.

On Friday I saw 3 question mark and 2 mourning cloak butterflies.

One of the question marks, named for the pale silvery small markings on the underside of the hind wing.

That in itself is not all that unusual, as I have seen both species at Mayslake before. What seemed odd was, in this butterfly-rich spring, these were the first of both species I have encountered on the preserve. Both overwinter as adults, and back in March during the warm weather we experienced, I would expect to have seen them, especially with multiple sightings of both species happening now. What gives? Yet another little mystery to tuck away in memory.

Literature Review: Monarch Navigation

by Carl Strang

If I had to choose one scientific journal to follow, it would be Science. Not only is this the most prestigious American journal (on par with Europe’s Nature), it is available at many public libraries and all college libraries. In addition to the original scientific papers published in Science, there is excellent reporting on results published elsewhere. Today I want to focus on one of the papers published in Science last year:

Merlin, Christine, Robert J. Gegear, and Steven M. Reppert. 2009. Antennal circadian clocks coordinate sun compass orientation in migratory monarch butterflies. Science 325: 1700-1704.

One of the wonders of nature in North America is the monarch migration. Each autumn, monarch butterflies from across eastern North America fly to a small area in the Mexican mountains and spend the winter there. They are removed by several generations from their ancestors who last made the trip. How do they navigate?

These three researchers looked at an aspect of this question. They knew from earlier studies that monarchs orient toward the sun to move in a southerly direction during their fall migration. Furthermore, the butterflies use a physiological clock (consisting of certain chemical reactions) to tell them where the sun is relative to south. This study found that the clock is located in the antennae rather than in the brain as had been thought. I would have guessed that persistent pheromones were involved somehow in monarch navigation, the butterflies perhaps following gradients of concentration with the aid of sensitive chemoreceptors in the antennae. It seems from this study that the antennae are indeed involved, but in a completely different way.

Early Insects

by Carl Strang

Large insects are beginning to appear at Mayslake Forest Preserve. For some weeks I have been seeing mourning cloaks, which overwintered as adults.

Mourning Cloak b

The above photo I took at Fullersburg last year. Another butterfly that overwinters as an adult is the eastern comma. This one at Mayslake apparently had a close call, probably with a bird. Note the missing section from the left hind wing.

Eastern comma b

There have been some orange sulfurs, which overwintered in the pupal stage.

Orange sulfur b

Their close relatives the cabbage whites have been common all over the preserve. Earlier  I celebrated the arrival of the first common green darner dragonflies, migrants from the South. The first locally emerging dragonfly I saw was this male common whitetail at Mayslake last week.

Common whitetail immature male b

He is recognizable to species and gender by his wing pattern, but he has newly emerged and so still has the immature coloration on his abdomen. The first mature Mayslake damselflies were eastern forktails.

Eastern forktail male b

The above photo of a mature male is from a few years ago, I believe at Songbird Slough, but this is our most common and widely distributed damselfly.

I have not had good luck photographing bumblebee queens this spring. Bombus impatiens has been common, and I saw one Bombus fervidus near the friary on May 22, at the same honeysuckle bush that hosted two of these:

Carpenter bee 2b

This is the large carpenter bee Xylocopa virginica.

The first monarch butterfly arrived at Mayslake this week.

Monarch 2009 1b

This individual is too clean to have made the trip all the way to Mexico and back. It is an offspring of those that wintered down there, made part of the journey back north, and laid their eggs on milkweed plants they found in the southwestern U.S. I shake my head in amazement at the instincts that guide these insects, with their pinhead brains, through journeys last made by their great grandparents.

First Dragonfly

by Carl Strang

 

Each year the first dragonfly species to appear in northeast Illinois is the common green darner. I saw my first ones this year at Mayslake Forest Preserve on a warm, sunny April 17 (this photo of a female I took in 2002).

 

green-darner-b

 

Males have blue abdomens. The bull’s eye pattern in front of the eyes is distinctive for this large dragonfly. Green darners we see in April are thought to have flown up from the south rather than to have emerged locally. This is a migratory species, though the ones that return probably are different from those that flew south in the fall. The leading current hypothesis is that migratory species like the green darner extend their breeding season and spread their genes over a wider geographic area. This makes sense of the fact that green darner nymphs also spend the winters in our ponds, and it appears that there easily could be a self sustaining local population. These early spring arrivals are getting a head start on the locals, which could include their own siblings, left by their parents before heading south.

 

So, this sighting does not allow me to list the common green darner as a breeding species at Mayslake Forest Preserve, but I will be surprised if it does not prove to have that status.

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