Bug o’the Week

A Snowbird Special Gulf Fritillary

Howdy, BugFans,

First of all, it’s a stunning butterfly https://bugguide.net/node/view/1734606/bgimagehttps://bugguide.net/node/view/1926994/bgimage (the BugLady’s picture doesn’t do it justice – the original slide, taken in Texas, was fine, but the scanned slide, not so much).  Second, unlike many of BOTW’s featured bugs, there was an abundance of information about this species, some of which sent the BugLady traipsing happily down a few rabbit holes.

This is not your grandfather’s fritillary (unless your grandfather is a Southerner).  Gulf Fritillaries are in the Brush-footed butterfly family Nymphalidae, along with a whole bunch of familiar Wisconsin butterflies, and they’re with the fritillaries in the subfamily Heliconiinae (which used to be its own family).  But, unlike our familiar fritillaries, they’re in the tribe Heliconiini, aka the Heliconians or Longwings, many of which occur in tropical climes and have long, slim, spectacular wings https://bugguide.net/node/view/1480877/bgpagehttps://bugguide.net/node/view/1478862/bgpagehttps://bugguide.net/node/view/309768/bgimage.  The larvae of many Heliconians feed on parts of passion vines and leaves, and the adults eat nectar of a number of flowers, plus fruit and sap, and many make or save toxic chemicals for defense.  Adults often spend the night in communal roosts https://bugguide.net/node/view/6260/bgimage (a group of butterflies is called a roost or bivouac).   

The Gulf Fritillary (Agraulis vanillae) (Dione vanillae in some books) is also known as the Passion butterfly because of its caterpillar host plant, and the Online Guide to the Animals of Trinidad and Tobago refers to it as the Silver Spotted Flambeau.  Carl Linnaeus gave it the species name “vanillae” based on a life cycle painting of the butterfly on a vanilla plant https://www.rct.uk/collection/921180/vanilla-with-gulf-fritillary done by the amazing 18th century naturalist/painter Maria Sibylla Merian, but the species doesn’t use vanilla plants.  If you’re not familiar with her, here she is https://en.wikipedia.org/wiki/Maria_Sibylla_Merian

Its range is described as Neotropical, which covers the ground from central Mexico and the Caribbean to southern South America.  In North America it is most common across our southern tier of states and the West Indies, and less so as you travel north http://mothphotographersgroup.msstate.edu/species.php?hodges=4413.  It’s one of the most common butterflies some in parts of Florida, where it has multiple generations per year; it was introduced to Southern California in the late 1800’s and is established there; it’s also established in Hawaii, and it has been recorded in Guam.  Gulf Fritillaries fly north in spring, breeding across the Southeast, and move back south again in fall, with Florida seeing dramatic migrations in both directions.    

It has a wingspan of two-and-one-half to almost four inches; females are larger than males and may have darker markings https://bugguide.net/node/view/666672/bgimage.

Courtship is exotic.  As a male and female circle each other in the air, he calms her flight response by releasing aphrodisiac courtship pheromones from “hair pencils” on his abdomen, and after she perches, he may hover above her, dusting her with more pheromones.  He perches beside her, they shift to face each other at a 45 degree angle, and he claps his wings open and closed, enveloping her antennae with each clap, delivering more pheromones from structures on the top side of his front wings and letting her know he is the same species (butterfly eyesight isn’t that great).  For Gulf Fritillaries, it’s “Ladies’ Choice” – females actively pick the males they mate with, so he really has to sell it. 

Rabbit hole #1: If she accepts his advances, his sperm packet, delivered when they mate, includes what’s called a nuptial gift.  The BugLady has written about nuptial gifts in spiders, katydids, tree crickets, and dance flies, but she had no idea that some butterflies produce them (they’re an energy-intensive investment for the male).  The sperm packet includes nutrients that will help her form eggs.  In the case of one of the European Comma butterflies (Polygonia c-album), the spermatophores are edible, containing both food and sperm, and the female, who mates with multiple males, can rate a male by the quality of plants he ate as a caterpillar (nettle is preferred) (Toto, I don’t think we’re in Kansas anymore).  

She lays her eggs, one by one, on or near a passion vine (purple passionflower has the best flower ever https://en.wikipedia.org/wiki/Passiflora#/media/File:OQ_Passion_flower.jpg), usually on the top surface of a leaf.  When they hatch, the caterpillars eat their egg shells – and sometimes neighboring eggs – and then start in on the leaves, often feeding in small groups.  

In the far southern US, Gulf fritillaries are in the air all year long, producing multiple generations.  They are said to overwinter as adults, but one researcher concluded that after passion vines die back in Florida in early winter, caterpillars can survive in diapause (dormancy – they halt development and resume when conditions improve).  They can also enter diapause in the chrysalis stage, though temperatures under 30 degrees are not good for them (or for most Floridians).  Here’s a nice series of a caterpillar forming a chrysalis https://bugguide.net/node/view/1589936/bgimage.  

Gulf Fritillaries are well-defended.  Adults can produce stinky fluids when alarmed.  The vegetation of many passion vine species is chock full of chemicals including glycosides that release cyanide when eaten, alkaloids, and strychnine and nicotine relatives, making their caterpillars a bad choice for predators.  And if that weren’t enough, the caterpillars are spiny https://bugguide.net/node/view/2047275/bgimage

Rabbit hole #2 was peripheral and was kind of like when you find out that deer eat baby birds (yes, deer eat baby birds, and so do chipmunks). 

In order to produce mating pheromones and “build” nuptial gifts, male butterflies in some species in the subfamily Danainae (the Milkweed and Glasswing butterflies) may want to boost their alkaloid load.  They can get extra alkaloids by scratching toxic leaves with claws on their tarsi (feet) and sipping the resulting sap, but researchers in the Sulawesi area of Indonesia noticed that some Danaine upped the ante by ingesting chemicals from caterpillars that had been feeding on plants in the dogbane family (which is closely related to milkweed).  Seven species were observed scratching dead or dying caterpillars and sipping the fluid (researchers don’t know if the scratching part had contributed to the dead and dying part).  They went after healthy caterpillars too (“subdued them” said the researchers), to harvest the toxic chemicals that the caterpillars sequester from their food plants for their own defense.  In their defense, it may be that the butterflies were attracted to leaves that were already scratched and oozing, and the caterpillars were just in the neighborhood.  Scientists had to coin a new term for this unique practice – “Kleptopharmacophagy” – literally “stealing chemicals for consumption.” 

One of the researchers, Yi-Kai Tea, referred to caterpillars as “essentially bags of macerated leaves; the same leaves that contain these potent chemicals the milkweed butterflies seek out.” Fortunately, our iconic Monarch has not (yet) been implicated in this behavior, which is a good thing because the BugLady wouldn’t be able to look one in the eye.

The great Roger Tory Peterson once said that a good birder always looks twice.  In his 1970 book Butterflies of Wisconsin, Ebner dismissed some early Gulf Fritillary records as “rather dubious,” and the Wisconsinbutterflies.org website lists it as a rare stray to the state.  Gulf Fritillaries are pretty distinct, but if you glance at a large fritillary and are about to write it off as another Great Spangled Fritillary https://bugguide.net/node/view/1990523/bgimagehttps://bugguide.net/node/view/1887246/bgimage, give it a second look, just to be sure.  

Kate Redmond, The BugLady

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