Not sure but it looks like a banded hairstreak to me.
Angie

Do they indeed eat grass?
-Jmcat

I dont really know I only seen a few and they seem hairyer than yours it could be a Gray hairstreak .The only butterfly I know thats eats grasses is common wood nymph,Ringlet,Little wood satyr but I never seen the cats to these might look them up.

The spot I found it on is under a maple tree; I don't know if it might have been eating that. We also have clover in our lawn, which might be a possibility. Right now, it's just sitting in one spot. I am wondering if it might be getting ready to molt.
-Jmcat

I got some leaves from a maple, grass, dandelion, elm, clover, and an unidentified shrub and put them in with this cat. It's currently crawling around, and I'm wondering if it might have eaten a tiny bit of the maple leaf, but I'm not sure. There was some wind today, so I really have no idea where it could have come from. At this point, I'm worried that this little guy is going to starve before I find out what it eats.
Thanks for the responses so far,
-Jmcat

It may have been wandering to look for a place to pupate. If that's the case, it probably won't eat anything. How large is the caterpillar. Hairstreak cats don't get very big. I've only had the gray hairstreak on my Hibiscus coccinea and it was very small when it pupated.

If it is a red-banded hairstreak, their host plants is leaf detritus, especially that of sumac.

Susan

It's about 1/2 inch long when stretched out. I have put in leaves from wild buckwheat, maple, clover, grass, lamb's quarters, alfalfa, prostrate knotweed, and an elm seed. This cat isn't moving right now, but it's currently rolled into a ball on one kind of grass, which is tall enough that I move it and disturb this cat each time I open and close the container.
I keep forgetting to mention that on each side of the cat's white line, there's a very thin maroon stripe that gets wider at the middle of each segment.
I checked the Red-banded Hairstreak (Calycopis cecrops), but my field guide says "Gray to brown...," and the picture it has is reddish gray. I also looked at a Banded Hairstreak (Satyrium calanus), but this field guide says: "Variable. Usually with darker blotches in front and at rear." and all three or so pictures I have seen of them show this darker area. This cat gets a tad darker toward the front, but not in the pattern I've seen; and it goes to brown at the posterior end.
Quite a few of the pics I've seen of Gossamer-wing caterpillars have white dorsal stripes, but on pretty much all of them there are either other prominent marks that aren't on this caterpillar, or, more often, there is a pair of white stripes instead of just one. At this point, I'm really not sure what to do.
-Jmcat

Or an American Copper? Will you raise it out to see?

The only reason I say American Copper is that it sort of looks like the pictures I have and it tends to be the most common around here.

Let us know?

Maryann in CT

Sorry, I forgot to mention I'm in Colorado. It doesn't look like the American Coppers (Lycaena phlaeas) are native here. I'm hoping to raise it, but I won't be able to until I figure out what it eats. I recall reading somewhere that most Gossamer-wings feed at night and hide during the day, which means that I likely won't know whether it likes anything I put in there until tomorrow.
Do Gossamer-wing cats just pupate in leaf litter? In one field guide I looked in, it had the cat length as about 1/2" for all members of this family, which would tend to indicate that it is about to pupate. However, I would think that it would have pupated by now if that was the case. Should I put something in the container with it for pupation?
Thanks again,
-Jmcat

Well, I think this cat may finally be deciding what to do with it's life! Amazingly enough, the decision doesn't appear to be to die. Looking at it now, it's spinning some silk, as if it was deciding to pupate! I still haven't seen it eat anything from the selection of leaves I put in with it, but at this point, I'm getting up hope that it won't die on me. I'll report back later about what it does.
-Jmcat

After I saw this cat spinning silk for pupation yesterday, I think I over-photographed it, as it them left the bit of enclosure it had made. It then started somewhere else where I couldn't see it very well, so I turned the container. I guess it must have been more sensitive after the first time, as it then moved out of there a little way. I placed a "shade screen" (made out of legos) in front of where it was, hoping that that would discourage it from moving again. I think it has more or less gone back to the second place and is doing more for the making of a chrysalis. However, I'll be very careful not to move the container at all until it pupates. I'm hoping that it will pupate here, and that I'll be able to see it as a butterfly for a more positive ID.
-Jmcat

I cant wait to find out what that guy is.

Yeah, I know the feeling!
-Jmcat

Well, the cat is a different color (lighter green) today. I couldn't tell for a while if it was alive or not, but I just saw it move slightly before I came over to the computer. Hopefully, it will molt tomorrow or sometime. Does anyone know how long Gossamer-wings (family Lycaenidae) stay in their chrisalides for generally?
Thanks,
-Jmcat

It seems that the longer I keep this cat, the more confused I get. It molted last night or sometime, but it isn't a chrysalis. It doesn't appear to be a caterpillar, either. I can't see anything that looks like a head, and I don't see any legs. It looks like a fat, segmented worm almost. It's a bit lighter of green today, and under the microscope, it seems to have dots of white in the green of its skin. Unless the chrysalides of Gossamer-wings move a lot as if exploring, I don't know any way that this could possibly be any stage of a lepidoptera. I'm going out of town tomorrow to Tuesday sometime, so you probably won't hear from me then.
-Jmcat

If it disappears and you start swelling at the abdomen ...

Nah.

Actually, I already thought of that.... We were going to be out of town tonight, but we decided that packing up from camping in snow wouldn't be much fun, so we just made it a day trip. Do you think I should just throw this guy out in the yard and let him fend for himself? For all I know, he could have been feeding on aphids or something, which I probably can't give him. On the other hand, then I won't know what he is just in case he might mature. He did spin silk or at least something that looked like it, which might be a clue as to what he is, but probably not much of one. Maybe I should post this over on the insect forum to see if they have any ideas.
Oh well. I guess if he dies, he dies, and I won't know what he is.
-Jmcat

Some caterpillars do spin silk to either 1) fasten the leaves together for a shelter; or 2) fasten themselves to a leaf for security. My HE's do this. In fact, they make their chrysalis on the leaf, as often as some of them climb a stick or the side of the container to pupate. I'd flip a leaf over in the container to check for a caterpillar and there would be a chrysalis, for gosh sakes!

Of course, this is the first time I've raised them. Your cat reminded me more of the "slug like" cats I've had, e.g., grey hairstreak. But then I've never seen an American Copper. Maryann in Connecticut has so many entomological resources at hand, I'd go with her ID.

Susan

Could it be a Hover Fly larva?

After looking at images on the net, I don't think it is a Hoverfly larva. The larvae are legless and wormlike, colored a dull green, with two narrow whitish long stripes about one-half inch long. Larvae are smooth-skinned and sausage-shaped. The head area is pointy and the tail looks like it's been cut off flat.

Susan

In that case, that sounds like a fairly good description! This larva, now that it molted, does not have any legs that I can see. It does seem to have a ridge on each side for the length of its body, and they are lighter in color. the head is fairly pointed, and its posterior end it fairly flat, except for a small, pointy bump that I can only see under a microscope. If it is a Hover Fly larva, though, that still wouldn't explain it before it molted, unless I carried this larva inside on one of the leaves and it ate the caterpillar. I don't recall actually seeing legs on it before it molted; I just assumed it did from how it moved. I don't know how I would explain it having a head capsule like a caterpillar, though, unless this thing did indeed eat the caterpillar.
Thanks,
-Jmcat

Here are two pics of what it looks like now. On the left is the skin of the caterpillar(?).
{{gwi:473440}}

{{gwi:473441}}

-Jmcat

Do hover fly larvae eat anything besides aphids? I've been looking for aphids, but haven't found any yet. Would it eat a leaf hopper?
-Jmcat

They are know to eat leafhoppers and thrips also, so give it a try.
-S.B.

After I posted my last post, I went outside and checked out one of our local salsify weeds (They always seem to have aphids on the buds!). Unlike the rosebush, which also usually has aphids on the buds, this plant had some aphids on it! They were black, rather than the regular green aphids we get, but they will hopefully still work. The only problem now is that this hover fly(?) larva is about as fast or slower than the aphids, especially since it hasn't eaten for a while. Do you think I should restrain (skewer) one of the aphids and put it right by the larva, or just let them go about their business? Another problem is that the aphids can easily climb the sides of the container, while the larva, being legless, can't.
-Jmcat

You might make a kill to get some nourishment into your larva. Also, you could try refrigerating your aphids so that they would be a little slower.

Sandy

I'm thinking of just throwing this guy outside at this point. I think it may be partially alive at this point, but it has a black area that is larger than yesterday (caterpillar equivalent of gangrene maybe?), and it's now a yellowish green rather than what it was before. Even if it isn't dying now, it seems to me that it's highly unlikely that it will survive at this point. Other people's opinions on the matter?
-Jmcat

Well, I think I'll keep it for a little longer at least. I just looked in the container I have it in, and I don't see 2 out of the 3 aphids I put in there yesterday. I suppose it's possible that they're hiding in the tiny bit of dried-up leaf in there, but I'm wondering if maybe they got eaten. So, I put 2 more aphids, this time green ones from a parsley flower stalk, in there.
-Jmcat

I would guive it a try, keep it for a while. It has a better chance of survivng with you because it has food delivered to it, and outside it will probably die from not catching any food since it is hungry, and has not had to much food.
S.B.