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biodiversity Butterflies and moths of Costa Rica Introduction non avian organisms

The Uraniidae moths are invading Costa Rica!

When birding Costa Rica and many other exciting, birdy neotropical countries with rain forest, one can’t help but notice a striking black and green moth that looks like a butterfly. It doesn’t look anything like the usual, amazing, hairy little beasts that show up at night lights and resemble miniature lost aliens. This beautiful creature doesn’t goes against the moth standard because the lepidopterists say that it’s mimicking swallowtail butterflies. I won’t deny that they resemble swallowtail butterflies in shape but its green and black coloration sure seems one of a kind. I mean it really does look more like some refrigerator magnet or sticker that shows a butterfly dreamed up by the design team of the Fukien All Purpose Happy Factory in China.

“Leung Chu, we have an order of 50,000 butterfly magnets for our biggest customer- the Dollar Store. Quick, design a pretty butterfly!”

“Sure Mr. Wong! That’s easy to do because all butterflies are pretty- how about this?” He shows a sketch of a black and green butterfly.

“Yes, that will be perfect!”

These Uraniidae moths look incredible but I have to admit that I have become habituated to feeling a bit let down when I see one because I think, “Now that’s one heck of a butterfly! Oh wait that’s right, it’s just a moth…”  I realize this a very discriminatory thing to do and I can’t justify it but all I can say in my defense is that the Urania moth tricks me. It throws me for a loop into thinking that I am watching some super cool, psychadelic butterfly instead of a mere masquerading moth. I really shouldn’t put it that way because I love seeing moths, especially the bizarre and beautiful creatures that make their appearance in the dark of the night, so I will attempt to overcome my feelings of betrayal and enjoy their presence.

That’s a pretty easy thing to do these days because the Urania moths are currently invading Costa Rica. I think the scouts showed up two weeks ago before the main drive on September 18th. On that day, while birding at Quebrada Gonzalez, a constant broad wave of Urania moths were flying in a general west to east direction over the canopy of the forest. The skyscape was littered with butterly-like moths and none were observed stopping to alight on the vegetation. The message must have also gotten out long ago about their bad taste because they were completely ignored by birds (of which we saw few due to the hot, sunny weather). I have also seen them up here in the Central Valley as they bravely (more dramatic sounding than the truth- hopelessly driven by blind instincts) flutter among the concrete and cinder block structures of Costa Rica’s urbanized sector.

Urania fulgens moths apparently undertake massive migrations like the one we witnessed once every eight years or so and might make it all the way to Colombia. In looking for information about their movements, I didn’t find as much as I had expected but did come across a paper written by Neal Griffith Smith who studied a migration of these awesome looking insects in Panama in 1969. He estimated that several million moths flew over the canal zone during Autumn of that year and hypothesized that they might migrate to take advantage of greater resources available to larvae during the wet season. Whatever the reasons are for the massive movements they make, judging by the small number of papers I found that investigate this moth, I don’t get the impression that the migrations of Urania fulgens have been studied very much.

If so few studies have been carried out on such a lovely, day-flying moth as Urania fulgens, just imagine how incredibly little is known about the majority of the fuzzy-antennaed creatures that flutter in the night and get eaten by owls (had to throw that last bit in- this is a birding blog after all).

Image of Urania fulgens at top is from Mike Quinn’s Texas Entomology website.

5 replies on “The Uraniidae moths are invading Costa Rica!”

Hi Pat,

I must comment on this moth since I almost mentioned it in my blog last week. I’ve never tried to get any information on it, so thanks for doing the leg-work! I too thought it was a butterfly, but it seems to me that I have seen it here each year in good numbers, flying first in one direction and then later (or earlier, I can’t remember which)flying back. You’re right, they don’t stop to feed.

See you one day near Turrialba. The volcano view from the Pacayas road today was just fantastic.

Paul Pickering

We are up in the hills by Puriscal.(Costa Rica)….witnessed a large migration heading from south to north. They looked like swallow tailed butterflies, but were green and black. Almost looked like they were fleeing the area before a storm.


I was in western Panama (Chiriqui province) last week and saw them. However, they seemed to fly ramdoly – perhaps because it was very windy most of the time? I remember seeing a large group flying eastward in the late 90s.


I am seeing them here in Portalon, south of Quepos and it is Mid-July. I too thought it was a butterfly.

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