Ants most definately eat butterfly eggs and 1st instar caterpillars (See below a section of an abstract). In fact, many plants, such as Senna, have what are called "extra floral nectaries". These are areas (usually little protruberances) that secrete nectar to attract ants. The ants in turn protect the plant from herbivores. There are lots of other things that eat eggs as well, ladybugs, tree crickets, lacewing nymphs. In addition, small wasps called chaclids, can lay their eggs inside butterfly eggs. This is why we often collect eggs and bring them to a safe place to raise. By the way, I have see a lot of chrysalises eaten by ants as well. They leave a nice neat hole, a little smaller than a pencil eraser. -Elisabeth Abstract I investigated variation in the effect of ants at extrafloral nectaries on the plant reproductive success among three populations of Cassia fasciculata (Leguminosae) in northern Florida. Results show that the possession of extrafloral nectaries can lead to increased reproduction. Density of ants and removal of experimentally placed Drosophila larvae were far higher on C. fasciculata than on nonnectariferous background plants. Ants preyed on eggs and small larvae of lepidopteran herbivores. C. fasciculata plants from which ants were excluded had more larvae of the major seed pod predator Phoebis sennae (Pieridae; Lepidoptera), suffered higher pod predation (at one site), and had lower reproductive output (at two sites) than did control plants to which ants had access. Effects of extrafloral nectaries on reproduction of C. fasciculata varied among the three populations, due apparently to differences in density of ants and potential herbivores.

Tiffany, I was reading one of the links given at Monarch Watch or Xerces Society, and some of the expert conservationist are hoping that Monarchs won't be declared endangered because then their hands are tied. Apparently getting anything done in an area where endangered species are involved is slow and complicated. I'm sure there was a simpler reason, but I was surprised that they preferred to stay "under the radar" in that respect. I wish I could remember their specific reasoning. Regardless, Monarchs need all the help we can give them. My husband released my first Monarch while I was out of town. It was from a caterpillar I got from my sister's garden. I have a brood of about 60 cats that are just starting to make their chrysalids. I had 23 in chrysalis form last night and lots more headed that way. Martha

I don't know the answer, but have experienced the phenomenon, too. In our case, it was the second or third of a very hot spell (around 100F, if I recall correctly). They left some milkweed growing under a potted tree in a large container in our side storage area. (Don't be deceived by the scale in the photo--the pot is 3'h x 3'w). I assumed it was the extended heat, but don't know for certain. I moved as many as I could to plants in a cooler location, because there was only concrete, and no other milkweed plants, in that area.

From what I can see in the photos, they look like syrphid fly larvae. These eat the yellow aphids, so are good guys unless you have Monarch eggs, which they may accidentally eat with the aphids.