Danaus plexippus - day 5

A few pics of the growing cats! Ages 3 and 5 days.

Danaus plexippus - day 4

I was reading a bit about caterpillar anatomy, so I got the little critters out and tried to spot some things. I'll throw out a few terms.

Here you can see two little knobs on the cat's head. At first I thought they were little spines, but they are actually the beginnings of the cat's front tentacles - simple sense organs. The back tentacles are even less obvious at this early stage.

In this photo it is possible to distinguish between the 3 pairs of "true legs" on the caterpillar's thorax, and the 5 pairs of "prolegs" on the abdomen. You can barely possible see, on the body segments holding the first couple of prolegs, the tiny holes called "spiracles" through which the caterpillar breathes.

The dark setae covering the caterpillar can be seen pretty clearly in this photo. If you compare them with those present on the older (by 2 days) cat in one of the images above, it appears that they become shorter as the cat gets older. The cats are all so small right now that it is virtually impossible to make out any other details on the head.


My source for terms, etc and a fantastic resource about Monarch cats is "A Field Guide to Monarch Caterpillars (Danaus plexippus)" by Karen Oberhauser and Kristen Kuda - Illustrations by Kristen Kuda, Department of Ecology, Evolution and Behavior; University of Minnesota; 1987 Upper Buford Circle; St. Paul MN 55108. It's available online as a pdf - a quick search should turn it up. There's quite a bit of useful info crammed into 16 pages.

Danaus plexippus - day 3

I almost crushed one of the babies today. When I went to change the leaf this afternoon, I saw one of the two smaller hatchlings crowling around on the side of their little container. What I didn't realize untill almost too late was that he was crawling around the lower part of the outside of the container. Luckily I realized just in time and returned him to a leaf!

It may not be easy to see in this photo, but if you follow Lincoln's line of sight there is a tiny day-old cat on the edge of the uppermost leaf. He somehow crawled up and over the edge of the plastic container behind him - very nearly making off across my dining room table. Why would he do that, when there was plenty of food inside there with him?

The older hatchling (only a couple days) is really becoming quite beautiful. He has assumed the pattern of stripes that he will have for the remainder of this phase of his life. Only his head still seems different from what I'm used to seeing on later instars - it is still black, though appears slightly smaller relative to the rest of his body than when he first hatched. I don't believe that he's molted yet, but perhaps I just missed it. 

I am glad they get bigger so quickly. I'm costantly fretting about crushing them by accident because I didn't see them. The one negative aspect of them growing larger is that the amount of frass produced by the older cat is exponentially larger than that of the younger ones. Eew.

A couple of thoughts about the early behavior I've observed. As a new hatchling, the cats seem to move around quite a bit. Very wriggly, and like I saw today, almost seeming to disregard the leaves in favor of running off. Is this because they are constantly in search of fresh leaves? Are they somehow more sensitive to leaf "staleness"? You may note in the above photo that the older cat is munching happily and voraciously on an older leaf, and is ignoring the fresher leaf next to him. But I did notice that the cats will often remain pretty still for periods of time, so perhaps this isn't really a factor. If this isn't the cause, are they attempting to distance themselves from their "egg leaf" for some reason? Or am I just really overthinking/imagining this?

Danaus plexippus - final eggs hatching!

Watching tv and working on homework just now, I decided to check if I needed to change leaves for the monarch. Quite to my surprise, the two remaining eggs that I was planning to watch hatch early next morning were already in the process of doing so! One had already emerged, eaten its shell, and was looking around for a meal. The other had only just begun munching his way free. Thanks to my camera and a magnifying lens, I've been held spellbound watching him. A really fun ending to something of a difficult day.

Muching a hole in the shell

Climbing out - I love how you can see the bite marks in the shell!

Eating the shell - an initial protein source. Wonder how they know?

My mom was asking me today, after looking at some photos, just how small these little guys really are (she won't actually look at them herself, and in any case I won't let anyone else near them). To give you an idea, I took this reference photo. The cat to the right is a new hatchling, and the one to the left is just a couple days old.

Keeping in mind that in a few weeks, these tiny guys will have become this:

Cool, huh? :)



Danaus plexippus - day 0 and day 2

I came home from school today to find my two remaining eggs turned the dark color indicating they will hatch soon.

I'm not sure if the caterpillar actually turns dark at this stage, or if it merely raises its head in prep. for hatching.

I also noted that the hatched caterpillar has developed his dark stripes this afternoon.

 

 

Danaus plexippus - day 2

Baby Danaus plexippus seems to be doing well. For all his eating (chunks of leaf large only compared to his tiny body) he doesn't seem to have gotten any bigger. I imagine I'll have to wait for his first molt to see that. But I am noticing a subtle color change. The places on his body where he was a creamy white, he is now starting to turn the green/yellow shade I'm used to seeing on monarch cats. He is VERY particular about leaves - I have to change them 3-4 times a day. I found him again this morning crawling away from a wilting leaf. I really should consider digging up a small plant and bringing it inside for him...

Danaus plexippus - day 1

Baby Danaus plexippus hatched yesterday morning before I got up. In the first image above, you can see the spot on the leaf where the egg used to be. It was eaten to provide the baby a first source of protein. Seems he was hungry - he ate a chunk of the leaf below it too! He wouldn't eat any more from the wilted leaf by the time I checked on him in the morning, so I had to bring him a new one. In the second image you can see that right now, during the early part of his first instar, the caterpillar is a dull white with several dark spines and a black head - the same that I could see the previous day through the shell.