Tuesday, September 6, 2016

Butterfly Invasion???

It isn't a butterfly invasion, but it is a butterfly migration!  This year the American Snout Butterflies are making their way down to the Rio Grande River area in mass numbers.
American Snout Butterfly, topside of wings.

American Snout Butterflies get their name from elongated mouthparts called palps that extend from the head.  They are small to medium sized butterflies (much smaller than a Monarch, also a bit smaller than a painted lady) and have orange and brown markings.  They blend in perfectly on bark and even flying can appear to be a leaf fluttering in the wind.

American Snout Butterfly underside of wings.
Each year, these guys make their migration, but their numbers are directly correlated with rainfall and moisture.  This year we had rain at the right times to help their population.  What the rain does is increase the leaves their host plant makes - the spiny hackberry.  With more food, the females lay more eggs in the summer and those eggs hatch and the caterpillars eat the new growth.  The caterpillars can really only eat new growth from the spiny hackberry because its tender enough for them to chew on.

This population explosion we are seeing is a result of those babies (caterpillars) becoming pupa and emerging to migrate down south.

Migration is often during late summer to early fall.  It isn't uncommon to see these large numbers, in fact we've seen in them in the not so distant past.

Expect to see them through the early part of fall.  In some years there are two generations before the fall is over, and I suppose time will tell if that will occur this year.

While they can be annoying and leave a mess of your car, there really no way to avoid them for the time being.  And you aren't killing them off - no matter how many you hit on your drive, there are still thousands upon thousands that will make it to their final destination.

Other butterflies you may be seeing mixed in with these are sulfurs and even some brushfooted butterflies.  But, by and large, if you notice large numbers of butterflies, you are seeing the American Snout Butterfly.

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