What you have observed are most likely NOT milkweed bugs. Can you describe this insect?

There are lots of other true bugs, especially nymphs, that resemble milkweed bugs to some extent.

From everything we can find on the internet it looks just like it with a heart shape on it back and two white dots lower on the abdomen. I will try to upload the photo I took of it, but I always seem to have trouble because of size or something.

can you see the photo?

Here is a link that might be useful: milkweed bug?

Yep, I can see the image just fine....and you are RIGHT! This is the Small Eastern Milkweed Bug. The thing about milkweed bugs is that they CAN feed on toxic milkweed, but don't always do so. I've seen them on my Echinacea seed heads, for example.

The behavior that I wasn't familiar with is that of feeding on another insect! (Which is why I doubted your identification.) But, sure enough, a quick search for Lygaeus kalmii led me to another image of this insect feeding on what appears to be a beetle. Don't know if this behavior is predatory or that of a scavenger.

Good for you for being so observant and for sending us a good image.

Here is a link that might be useful: click here to see!

It is cool to see something that isn't seen very often and why I too doubted what I was seeing. We were at the plants squishing shield bug nymphs, but I think the milkweed bug already was feeding when we saw it, though we could have squished one earlier that it decided to have for dinner.

Thanks rhizo 1 for you help!

Christine

Thank YOU.

I live in Los Angeles, and I noticed yesterday
morning (06 May 2015) a line of ants on my rear garden path. They led
to a dead milkweed bug. Nearby was a live milkweed bug that was staying
away from the ants and not being bothered by them.


Later in the morning, I noticed the ants were gone. The corpse of
the bug remained, as did the live one that I presumed was a mating
partner. (I have seen many mating pairs the last month or so, and we do
have milkweed growing along the concrete path where I spied the dead
bug.)


Throughout the day, the live milkweed bug remained with the dead
one, often not even scurrying away as I stepped over them. In the late
afternoon, I finally stopped to investigate. The live one ran to the
edge of the concrete and turned, standing high on its legs and watching
me.


The dead bug was intact—at least its exoskeleton and wings were—but
it was stuck to the concrete as if something had been squished out of
its abdomen.


This morning (07 May 2015), and just minutes before I wrote this,
the live one (presumably the same one all this time) remains with the
dead one. No more ants, although they are nearby along the edge of the
concrete.


I had to comment as this behavior appears remarkable. Are these
milkweed bugs monogamous, or perhaps cannibalistic, or what? I find it
odd that for more than 24 hours, the live milkweed bug has remained at
or near the dead one's side.

Below is a photo of the dead one with what appears to be an aphid (also dead, and apparently dehydrated or dessicated) to the upper right. I tried to get a shot of the two, but the live milkweed ran whenever I approached and stopped to photograph both.