The Monarch caterpillar feeds almost exclusively on Milkweeds from which it absorbs a toxin, cardiac glycosides. This makes the adult butterfly poisonous, or at least very distasteful. Predators learn this fast. One or two might get eaten and spit out, but the rest get a free pass to the mountains of central Mexico. A few other butterflies have apparently evolved to mimic the Monarch, the closest copy is probably the Viceroy, which is very similar to a smallish Monarch except with a black line across its hindwing. I believe its range could put it down here, but I have not seen one.
Here is a hierarchy of some butterflies I did photograph today.
Queens are all over south Texas. Close-winged they look similar to a Monarch, though noticeably smaller. Open-winged the ribs are not noticeable and to my eye they are brown rather than orange-tone.
There are 73.2 Queens for every Monarch in Hildago County. Give or take.
That famous migrator, her majesty the Monarch, is the toughest, strongest butterfly in North America, maybe in the world. Some butterflies have wings so thin they are a wisp in the air and are wind tattered in a matter of a day or two. The Monarch hindwing exteriors are cream, the rest of the wing surfaces are a rusty orange with black ribs visible inside and out.
Factoid: It is a little known fact that the Monarch wing is actually made of 3-ply birch plywood.
And for every 37.3 Monarchs there is one Soldier. I guess that makes them fairly rare and local. I saw a couple today that I took to be Soldiers, not positive but leaning strongly in that direction. I think I read that the Soldier caterpillar also feeds on milkweeds so it probably tastes like a Monarch too.
And just for the name, I will throw in an Admiral. A beautiful thing, spread or closed.
Getting late, goodnight - Gunnar