Murray is So Tall

Murray is definitely long for his age. He measures a whopping 3 cm (or 30 mm) in length. According to the U. of Minnesota’s Field Guide to Monarch Caterpillars, fourth instar caterpillars should measure from 13 to 25 mm in length.

Fifth instar caterpillars should measure from 25 to 45 mm. His front tentacle measures 10 mm which is the right length for the fifth instar.

Close-up

So which instar is Murray?

He definately exhibits those white markings on his legs as you can see in both photos. (Click on them to see close-ups.) I have found him walking up the side of the jar so is he seeking a place to pupate? The length of his body and front tentacles are pretty long. that all seems to add up to him being in the fifth (not fourth) instar.

Monarch caterpillars go through five instars (the period between molts). He stopped eating early today and lives attached to the underside of the leaf – this is the second time I have observed this behavior and indicates the beginning of the molt.  Murray is molting now (no photos since I do not want to disrupt the event – he is most vulnerable during the molt).

White Spot on Leg

I think Murray is entering his fourth instar based on his size and time since he “hatched” from his egg. There are supposed to be distinct white spots on his forelegs during the fourth instar and one of the photos from yesterday shows a small white spot probably indicating the third instar  (click on the photo to see a large version – the white spot is visible on the first leg from his head).  Also, Murray showed the typical third instar eating behavior – a cutting motion on the leaf edge which you can clearly see in yesterday’s close-up. But what do I know; this is my first monarch midwifery.

During the fourth instar, those white spots should be conspicuous. When he starts eating again, he should be even more hungry – I will measure him then and compare with the “official” stats.

Murray is Browsing

I changed his leaf and emptied the water jar (with his poop inside). He is growing and slowly wanders around his kingdom.

In this photo, you can see the caterpillar’s head capsule (the two semi-circular portions at the upper portion of the head).

In the center is the mandible and you can see the spinneret near the leaf surface (click on the image to enlarge it). Murray will be in the caterpillar stage for about two weeks and grow to about two inches long.

You can see his home in the last photo. There is a large outer jar covered with mesh. The smaller inner jar has water to keep the milkweed leaf alive. Murray is somewhere on the leaf (he likes the underside the best).

Murray's Home

Close-up