12 September 2014

Guest Post: Mystery Butterfly


Yesterday a butterfly I’d never seen before visited my yard. It had the colors of a swallowtail, but no tails, and it didn’t match anything I could find by doing a Google image search for “black and yellow butterflies." So I posted a (low-resolution) smartphone photo to Facebook and got an immediate reply from a cousin in Wisconsin--“Could it be a Mourning Cloak?” Though the Mourning Cloak is Montana’s state butterfly and does frequent my yard--and its general morphology is somewhat similar--I’d already ruled out Mourning Cloak using the eNature.com online butterfly field guide.  

However, eNature was no help in figuring out who the mystery visitor actually was. The categories I might have chosen from their list--swallowtails or “boldly patterned”--produced no results. This was a very cooperative butterfly, however, hanging around all day and posing prettily on the bee balms (Mondarda sp.) that have proliferated where the native vegetation catches overspray from the lawn sprinklers. So I was able to get several good shots with a real camera, and e-mailed one to my friendly local naturalist at the Montana Natural History Center, Brian Williams. 

Twelve hours later, I had a reply: “Hi Kim, Great picture and good butterfly--it's a female Great Spangled Fritillary. Charles [Miller] and I were out in the Rattlesnake yesterday and saw one ourselves! Perfect timing on your question too, I've been working on my fritillary ID skills the last two weeks.” 



Here are views of the undersides of their wings: Male:

and Female:



He responded: "Well, identifying the fritillaries besides Great Spangled is my summer's million-dollar question. Luckily, the Great Spangled is the one (of 10 or so, it seems), that is most readily identified. The best characteristic is the nature of the silver spots on the bottom of the hindwing--in the Great Spangled, the spots are relatively few, small, and well-spaced compared to all the rest of the fritillaries (like your photo, which is indeed a Great Spangled). The Great Spangled is also a bit bigger than all the other fritillaries. So, while at first glance, the Northwestern and Hydaspe Fritillaries are similar to Great Spangled in overall color, it is possible to distinguish them in the field. Beyond Great Spangled, the question is much more muddied. Charles and I have been collecting fritillaries for a display and I've actually been submitting photos of our pinned specimens to the website 'Butterflies and Moths of North America' to get positive identifications. Good fun!"

(Now we know what naturalists do when they aren't leading field trips!) 

Natural History Information from the Butterflies and Moths of North America Website
Great Spangled Fritillary 
Speyeria cybele (Fabricius, 1775) 
Family: Nymphalidae 
Subfamily: Heliconiinae 
Wing Span: 2 1/2 - 4 inches (6.3 - 10.1 cm).
Caterpillar Hosts: Various violet species (Viola). 