Bill Dunson Bill Dunson

A tiny legume destroyer- the Genista moth

Another one of those things that go on in our backyards without much notice is the occasional destruction of plant leaves by small caterpillars. Sometimes we get annoyed by this and spray the plants or try to figure out what is happening. In recent walks in scrub habitat at Lemon Bay Preserve I have noticed that many of the beautiful sky blue lupines, which are not yet in bloom, are being heavily damaged by a small caterpillar (see photo attached). I was unfamiliar with this species and searched the web to find out that it is well known as a destroyer of various legumes, including lupine and members of the genus Sophora which includes necklace pod in Florida.

The rest of the story is that this caterpillar is immune to the powerful toxins found in legumes, and indeed uses these poisons to defend itself against attacks by predators. If this reminds you of some other famous cases think about monarchs and milkweeds, and zebra butterflies and passion-vines. So here is another case of a larval insect stage making itself toxic by eating a poisonous plant. Consider what this means- that the ability to tolerate the toxins must have evolved over a very long period, and then coloration advertising the toxicity (aposematic or warning coloration) developed. Then predators must recognize the significance of the warning coloration, perhaps specifically or generically. Some predators such as lynx spiders apparently can handle the toxins and eat the caterpillars

(see this article).

Now the adult is distinctively colored (see photo from web) but I do not know if it is protected also.

So if we needed reminding that the natural world is amazingly complex and interesting, here is another case. The deeper we look the more we see, and the more impressive the web of life becomes. So get out there and groove on nature but don't eat the caterpillars!

-Bill Dunson, Englewood, FL

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Bill Dunson Bill Dunson

A tale of 2 "nutty" butterflies- the buckeyes

Lemon Bay Preserve in southern Venice, FL, is an interesting place for many reasons, but it has some remarkable butterflies illustrating the role of habitat differences in speciation. For example during a nature walk there yesterday we saw a mangrove buckeye butterfly in a tidal area sitting on some saltwort (see photo). The name is a bit strange since the buckeye tree does not occur here; the tree is named for its large brown nuts which somewhat resemble the eye of a deer/buck. Indeed this butterfly does have 6 distinctive eye-spots, likely useful in deterring predatory birds. Buckeye butterflies often sit in open areas with their wings spread, allowing an observer to admire their unusual coloration. What really excites me about buckeyes at Lemon Bay Preserve is that there are actually two different but closely related species there, the mangrove and common buckeyes. The other photo shows a common buckeye that I found there on another day. If you look carefully you will notice some subtle but distinctive differences between these two sibling species.

The common has lighter or even white borders to the large eye-spot on the fore-wing; in addition the two eye-spots on its hind-wings are much more different in size than in the mangrove buckeye. While these differences are clear, they are not so striking that it is that easy to recognize them in the field.

So what is going on here? How can two closely related species co-exist in the same area without competing? The common buckeye is by far the most widespread in N. America (larvae feed on gerardia, toadflax & plantain) whereas the mangrove buckeye, as its name indicates, is primarily limited to the sub-tropical tidal coastline, and its caterpillar feeds mainly on black mangroves. This situation illustrates one mechanism by which new species originate- habitat specialization within one species splits off a separate species. Whereas speciation normally requires considerable geographic separation, the degree of isolation here is very small and due to juxtaposition of two distinctively different habitats (saline mangroves and adjacent uplands). Sometimes the argument is made that evolution is hard to observe, but here in our backyard we can actually see the end results among two "nutty" buckeye butterflies!

Bill Dunson

Englewood, FL & Galax, VA

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