Mayslake Update: Insects

by Carl Strang

The warm weather has brought out a beautiful diversity of insect life at Mayslake Forest Preserve. Here’s the gallery from last week:

Early zanclognatha moths are appearing in good numbers this year in Mayslake’s woodlands.

Early zanclognatha moths are appearing in good numbers this year in Mayslake’s woodlands.

Here is a second one, showing some of the variation in this species.

Here is a second one, showing some of the variation in this species.

What they have in common is their relatively early season compared to similar relatives, a rather sharp bend in the dark line closest to the head, a kink or at least flat area in the tip of the curve in the middle line, and a rather straight outermost line. This is one of a large group of moths whose larvae make their living by eating dead leaves. Many are common in our woodlands thanks to that abundant resource.

This skipper put me through a long session with the references. I concluded that it is Juvenal’s dusky wing.

This skipper put me through a long session with the references. I concluded that it is Juvenal’s dusky wing.

It is very similar to the wild indigo dusky wing, which also occurs at Mayslake, and I need to be more careful in the future in identifying these butterflies. The difference, as I understand it, is that Juvenal’s has areas of pale color within the black inner part of the forewing, and just inward of the central tan area there is a pale dot (very faint in this individual) rather than a short bar.

Less ambiguous is this Virginia tiger moth. There are other white tiger moths, but they don’t have the fancy black-and-white barred legs, a couple of which are sticking out here. Also, this one patiently let me move its leaf so as to get a look at its front femurs. They were yellow-orange rather than pink.

Less ambiguous is this Virginia tiger moth. There are other white tiger moths, but they don’t have the fancy black-and-white barred legs, a couple of which are sticking out here. Also, this one patiently let me move its leaf so as to get a look at its front femurs. They were yellow-orange rather than pink.

This pretty little moth, photographed near the edge of the north savanna, was an addition to the preserve species list. The spotted grass moth is described as “uncommon” in references.

This pretty little moth, photographed near the edge of the north savanna, was an addition to the preserve species list. The spotted grass moth is described as “uncommon” in references.

Viewed dorsally, this Laphria thoracica robber fly is a very effective bumblebee mimic. At this angle, however, we can see how it is alertly watching for passing prey. The flattened abdomen, impressive predatory beak, and odd antennae prove that this is no bee.

Viewed dorsally, this Laphria thoracica robber fly is a very effective bumblebee mimic. At this angle, however, we can see how it is alertly watching for passing prey. The flattened abdomen, impressive predatory beak, and odd antennae prove that this is no bee.

First spreadwing damselfly of the year. The southern spreadwing is regarded by some as a subspecies of the common spreadwing.

First spreadwing damselfly of the year. The southern spreadwing is regarded by some as a subspecies of the common spreadwing.

Mayslake Lepidoptera Update

by Carl Strang

Recently I provided an update on damselflies and dragonflies that have become active at Mayslake Forest Preserve. New butterflies and moths also have been appearing. The large group of butterflies known as skippers can be tricky, but I believe I have these right: Hobomok skipper,

Hobomok skipper b

and tawny-edged skipper.

Tawny-edged skipper 2b

Both are, according to my references, common. I have found Hobomoks in other preserves early in the season. Even more common and distinctive are two more species, the least skipper

Least skipper 2b

and silver-spotted skipper, the latter never far from black locust trees.

Silver-spotted skipper b

The most recent butterfly to show itself has been the spring azure.

Spring azure 2b

Moths also are in evidence. This one, Zanclognatha cruralis, belongs to a curious group whose larvae eat dead leaves.

Zanclognatha cruralis b

The following moth I photographed on the slope between May’s Lake and the friary, not far from a large white pine.

Semiothisa bisignata cropped b

This one proved to be a tough ID. There is a large group of moth species which look very much like this one. Furthermore, many of these species show considerable variation among individuals. The yellow head and anterior thorax are unusual among them, I gather, and help to narrow down the possibilities. My tentative identification is Semiothisa bisignata, the caterpillars of which eat pine needles. In the future I may need to collect one or more of them. With some insects, photographs simply aren’t enough.

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