Breaking: Mexican Silverspot Butterfly Sighted in Colorado

Right place, right time, and with a little help from your friends. That is how discoveries are made. All of those factors came together to verify the spotting of a Mexican Silverspot butterfly, Dione moneta on the eastern edge of Colorado Springs, Colorado on April 18, 2017.

Sharon Milito is a geology lecturer at University of Colorado, Colorado Springs, and a retired Colorado Springs School district eleven teacher. She has also been a volunteer with the city for ten years, doing paleontology surveys and acting as a science education consultant. She has, in her volunteer capacity, access to places not open to the public, including Jimmy Camp Creek Park on the very eastern edge of the city.

Sharon and I went scouting on Tuesday, April 18, and she took me to specific locations that seem to have a slightly greater biological diversity in the sprawling former ranch. It is a unique composite of many different habitats including mostly shortgrass prairie punctuated with sandstone bluffs. Some of the bluffs are covered in Ponderosa Pine forest. There is also Jimmy Camp Creek itself, a drainage fed by numerous springs within the property. There is almost always water in the creek, and some surprisingly deep pools in the sandstone bed. Otherwise, lots of mud trampled by cattle that still graze the park.

One of the areas we went to boasted a grove of wild plum, Prunus americana, in full bloom. It was like walking into a fairy tale. Hundreds of butterflies were sipping nectar from the blossoms. Most were Painted Lady, Vanessa cardui, but there were also Red Admiral (Vanessa atalanta), Milbert's Tortoiseshell (Nymphalis milbertis), Gray Hairstreak (Strymon melinus), Marine Blue (Leptotes marina), and several Monarchs (Danaus plexippus). Most of the Monarchs seem to have had a rough migration up from the south. The whole morning scene was mesmerizing and enchanting.

Eventually, Sharon called me over to ask "what about this one here?" and pointed out a butterfly that had me perplexed initially. At first I thought it was a Variegated Fritillary, which would be expected at this time of year. The wing shape was a little odd, though, and when I glimpsed the underside, it was studded with large, silver spots. Wow, a Gulf Fritillary. That is not a very common butterfly in these parts. I got several images of the insect and we went our merry way. Later, I posted what I thought was our somewhat significant find to the Facebook group "Arthropods Colorado" for more folks to enjoy.

Enter Robb Hannawacker. He raised the stakes substantially higher by proposing that the butterfly was in fact a Mexican Silverspot, Dione moneta. I was embarrassed to admit that until he mentioned it I was not even aware of the species at all, let alone where it is supposed to occur. Robb mentioned the identifying markings, and how our specimen matched them, and it is now pretty obvious that is what we have.

According to my copy of the Kaufman Field Guide to Butterflies of North America, the Mexican Silverspot "Strays to south Texas, rarely to southwest and Big Bend region. More at home in mid-elevation tropical woodlands but reported to breed sporadically in lower Rio Grande Valley....Recorded late spring to late fall (multiple broods in Mexico." The butterfly['s normal range extends from Mexico through Central America to Brazil. The larval foodplants are passion vines, which do not occur in Colorado.

The most recent northern record for the species in the online database of Butterflies and Moths of North America was on May 8, 2005 in Roosevelt County, New Mexico, by Christopher Rustay. As near as I can tell, this is the first record for Colorado, at least of recent vintage. Please alert me to additional historical records. Thank you. Now, go forth and see what amazing species you can find.

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.

The Monarch Dethroned

I confess I have come to dislike the Monarch butterfly, Danaus plexippus, but it has nothing to do with the lovely insect itself. My objection is to the public obsession with the species to the exclusion of so many other butterfly species, let alone moths and other insects. It is also a manufactured obsession created by the many conservation groups that have capitalized on the Monarch’s existing popularity and used it to generate revenue for their organizations.

Let us explore some of the myths that have been purported as a result of the propaganda produced by the likes of Monarch Watch and the Xerces Society, whether accidental or intentional.

Monarch butterflies are important pollinators. The overwhelming majority of butterflies are poor pollinators. They belong in the category of “flower visitors” since their primary goal in alighting on blossoms is to obtain nectar, not pollen. Nectar is rich in carbohydrates that fuel the flight of many insects. Pollen, on the other hand, is rich in protein suitable for the growth of immature insects like bee larvae that have the chewing mouthparts to crack the pollen grains. Butterflies, with their siphoning mouthparts, cannot chew the grains, but the adult insects have little need for protein anyway. Bees, many moths, flies, certain wasps and beetles are far more important pollinators.

Genetically Modified Organisms (GMOs), especially crops, harm Monarchs. Monarch caterpillars feed only on milkweeds, so they are not coming into contact with genetically modified crops. There may be a grain of truth in suggesting that Roundup Ready crops immune to herbicides have led to a decline in milkweed plants in agricultural settings. Credit should go to Monarch Watch for promoting the cultivation of milkweeds in urban, suburban, and rural settings not subjected to herbicide use. There may be other reasons to dislike GMOs, but killing butterfly caterpillars is not one of them, at least in this case.

Monarch populations are crashing. Populations of many species of insects have boom and bust cycles, and I strongly suspect the Monarch is one of them. There is reason for concern regarding their wintering grounds in the mountains of Mexico, where illegal logging and irresponsible ecotourism definitely contribute to mortality of these insects. The adult butterflies are probably not very plastic in their ability to adapt to other potential wintering groves, if there are even any left standing. Once the butterflies nestle in for the winter, they are vulnerable to disturbances that startle them into flight and burn their fat reserves prematurely. Ecotour operators need to be evaluated to insure they are responsible in their visits to butterfly roosts.

Still, conservation organizations may be guilty of creating a perpetual crisis that does not exist in reality. Were Monarch numbers declared stable, there would be no perceived endangered status, and monetary donations would dry up. This “sky is falling” phenomenon is probably true of many environmental organizations, and one should be wary when deciding where to spend one’s disposable income.

All of this is not to say that the Xerces Society, Monarch Watch, and other non-profits are not doing valuable work, or are merely exploiting human sentiments for “poor butterflies.” Indeed, Xerces has branched out over recent years to address insect conservation beyond butterflies, such as protecting aquatic insects and native pollinators. Also, exaggerating an organism’s endangered status can be a way to draw attention to an otherwise overlooked or understated issue.

The biggest problem I personally face in promoting insect conservation is in getting the public to think “outside the chrysalis” if you will, and recognize that arthropods other than butterflies are valuable. It is incredibly important to change public attitudes toward wasps, spiders, and flies, for example.

We are making collective headway in creating popular movements that embrace dragonflies, damselflies, moths, and (to a lesser degree) tiger beetles, that do not involve collecting specimens. So, I remain cautiously optimistic that the trend will continue. Just don’t ask me about Monarchs.