Mourning Cloak

I have neglected butterflies on this blog for the most part, as there are plenty of other blogs about them, books and websites, too. Plus, let’s face it: they are easy to love. My general mission is to stir a passion for other insects and invertebrates. That said, at this time of year along the Front Range of Colorado, certain butterflies are the most obvious of insects. The Mourning Cloak, Nymphalis antiopa, is also admirable for its sheer durability.

This butterfly is one of the “tortoiseshell” butterflies, a subgroup of the family Nymphalidae, collectively known as “brushfoots.” Look at any nymphalid and it looks like the insect has only four legs instead of the customary six. The front legs are greatly reduced in size and drawn up close to the head, where they function more like extra mouthparts than legs. The female butterfly scratches leaves with those tiny legs, causing the plant to produce volatile compounds that the butterfly analyzes to make sure it is a proper host plant on which to lay her eggs.

Tortoiseshell butterflies overwinter as adult insects, crawling into crevices and cavities in logs, stumps, and other protected spots. A warm winter’s day will see them taking wing, before going back into hiding until early spring.

Once a Mourning Cloak emerges from hibernation, it seeks sustenance to fuel its flights. A favorite source of nourishment is sap oozing from wounded trees. Indeed, a sap flux can quickly become a mecca for these butterflies, as evidenced in the short video below. They are amazingly tolerant of each other’s company considering their usual behavior.

Male tortoiseshell butterflies are highly territorial, each one staking out a patch of real estate that it defends vigorously from other males, and even from other species. I say many a battle between a male Mourning Cloak and a male Hoary Comma on April 11, the day I shot most of these images along a riparian trail near the Bear Creek Nature Center in Colorado Springs. The insects would often literally bang into each other during their aerial dogfights.

While males quickly become tattered and exhausted, females, once mated, set about to find suitable host plants on which to lay eggs. You will find the Mourning Cloak to be most abundant in willow thickets, as Salix spp. are the favored hosts. Caterpillars will also feed on elm, birch, poplar, hackberry, rose, mulberry, and other trees and shrubs to a lesser degree.

Large masses of eggs, typically 100-200, are laid by the female, the ova encircling a branch or twig. The caterpillars pass through five instars (an instar is the interval between molts), eventually topping out at about 5 centimeters (two inches) in length. Black with white speckles and maroon spots, the larvae are studded with spikes.

They occur in large groups, so when you find one you will usually find several more nearby. During their younger instars they share a loose, tent-like web for protection from predators and parasites.

By June or July another generation of Mourning Cloaks is on the wing. There may be two generations in the southern reaches of this butterfly’s range, but at higher elevations and latitudes there is but one generation produced each year, fresh adults emerging in late August or early September.

The Mourning Cloak is holarctic, meaning it is found throughout the northern hemisphere. In Britain it is known as the “Camberwell Beauty.” Here in North America, it ranges from Alaska to Mexico, and the Pacific Coast to the Atlantic seaboard.

Few insects live as long as a Mourning Cloak in the adult stage. On average, they survive 10-11 months, though much of that is sequestered in a hibernaculum. They are always a welcome sight, and a true harbinger of spring if ever there was one.

Sources: Brock, Jim P. and Kenn Kaufman. 2003. Kaufman Field Guide to Butterflies of North America. Boston: Houghton Mifflin Co. 384 pp.
Ferris, Clifford D. and F. Martin Brown. 1980. Butterflies of the Rocky Mountain States. Norman: University of Oklahoma Press. 442 pp.
Pyle, Robert M. 2002. The Butterflies of Cascadia. Seattle: Seattle Audubon Society. 420 pp.

Wasp Wednesday: Winter Wasps

Perhaps I should call this entry “early spring wasps.” We have had a very mild winter here in Colorado Springs, Colorado, and it seems that spring comes earlier and earlier now, no matter where one lives. Certainly more southerly latitudes are experiencing spring right now. Still, I am amazed by the wasps I am finding on the wing already.

While out hiking an urban trail on February 29, I found female Podalonia cutworm wasps out and about in the 58°F temperature. Perhaps they were hunting for those Army Cutworm caterpillars that have also been roaming on warm days. One of the wasps I observed was digging, but I could not discern whether she was excavating a burrow for prey she already had, or was unearthing a moth larva.

A few days previous to Leap Day, Heidi had brought me a wasp that she found flying around one of the exhibits in Primate World at the Cheyenne Mountain Zoo where she works. She had already correctly assumed it was an ichneumon wasp. Many species in the subfamily Ichneumoninae overwinter as adults, sequestering themselves under bark, deep inside rotten logs, and other protected situations. Unfortunately, I didn’t get around to imaging this specimen (below) until after it had expired, but in my defense it is very difficult to differentiate a wasp in torpor (a state of greatly reduced metabolism) from a deceased one.

Social wasps like yellowjackets and paper wasps also overwinter as adults, though it is almost exclusively females that do so. So, I was not completely surprised to find Western Paper Wasps, Mischocyttarus flavitarsis sipping water from melting snow in a narrow arroyo in Red Rock Canyon Open Space on March 5. The high temperature on that day was 68°F.

Any female paper wasp has the potential to be the “foundress” of a new colony, so most of the females survive the winter. Only yellowjacket queens are capable of reproducing, so you will find no workers until summer. I would expect to see queens of some species out by the end of March in most places, but here at higher elevations they seem to wait much longer to emerge. Can’t blame them, as blizzards in April are not uncommon along the Front Range.

One wasp that really did surprise me was another specimen I encountered in that narrow dry arroyo. My initial observation led me to think it was a spider wasp (family Pompilidae), but I was able to get fairly close to it and get some respectable images. Turns out it was a wasp in the family Crabronidae, tribe Larrini. Members of this tribe prey mostly on crickets or grasshoppers. Considering that there are indeed grasshoppers out already, too, I guess I shouldn’t be surprised.

I’m still awaiting help to identify this wasp more specifically, but my guess is that it is probably in the genus Liris. Watch this space for updates in the comments, but don’t put your life on hold. These things take time.

Oh, I almost forgot! Just yesterday, a warm and windy 69°F day, I encountered yet another wasp on the Rock Island Trail near the intersection of Constitution Avenue and Academy Boulevard. Yes, this is pretty urban territory, paralleling an old railroad bed. What should come scurrying across the concrete path but a velvet ant (family Mutillidae). Female velvet ants are wingless wasps that, as larvae, are parasitic on other insects. They are often found digging open the burrows of other solitary wasps.

My friend Justin Schmidt thinks the assumption that velvet ants don't survive the winter may be incorrect. He is currently conducting catch-and-release experiments to see if he can find the same females in autumn and the following spring. The specimen I found is clearly encrusted with soil, suggesting she recently emerged from underground. Whether she emerged from a pupa or a hibernaculum is open to speculation.

The weather here is supposed to take a turn for the colder over the next few days, but bounce right back up into the low 60s early next week. I’ll be interested to see if the insect and spider populations skip a beat, but I doubt they will. One has to appreciate the endurance and resilience of insects, if nothing else about “bugs” is admirable.