Weidemeyer's Admiral First Instar

First instar Limenitis weidemeyeri latifascia caterpillar on its perch.

First instar admiral and viceroy caterpillars do not measure length of day to determine whether or not they will construct a hibernaculum and hibernate at third instar.  This measurement takes place as soon as they molt to second instar.  Therefore, if you ever find a first instar viceroy or admiral caterpillar, it is advisable to set it up in a semi-closed terrarium and then expose that to 24 hours of light so that you can emerge an adult within 30 days or so as opposed to wintering the larva and waiting for the next spring.

Viceroy First Instar Caterpillar

Limenitis archippus lahontani first instar caterpillar on its perch.

Arizona Sister First Instar Caterpillar

This is a photo of an arizona sister (Adelpha eulalia) first instar larva that has extended the vain an oak leaf (Quercus turbinella) with dung pellets; creating a conspicuous perch where the larva rests. 

When looking for first, second, or third instar caterpillars, it is not that hard to train your eye to look for these perches.

Arizona Sister Second Instar Caterpillar

Weidemeyer's Admiral First Instar Caterpillar

Here is a Limenitis weidemeyeri latifascia first instar caterpillar on chokecherry (Prunus virginiana) set to molt to second instar.  This video describes how I was able to find this caterpillar in the wild.

Lorquin's Admiral Third Instar Caterpillar

Arizona Purple Third Instar Caterpillar

Lorquin's Admiral Third Instar Caterpillar

Lorquin's Admiral Third Instar Caterpillar

Same caterpillar as previous slide; but shot in nature along Silver Lake, Snohomish County, Washington.