Samia ricini Larvae Molt into Fifth Instar

Our oldest eri caterpillars (Samia ricini) molted into fifth instar. These are offspring of Europe sourced sibling-paired adults from a previously reared brood and have been reared indoors on citrus (Citrus).

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Several of the  Samia ricini larvae ​that were in apolysis molted into fifth instar after spending 18 days in fourth instar (four of which were spent in apolysis). They are all slightly different sizes, though the largest are at 0.9 g. Below is a compilation of me lapse photos of one of them molting.

Below are anterior and posterior views of a teneral fifth instar. The head is protruding more than it normally should and the anus looks swollen due the larva pumping air into its body to stretch the cuticle before it dries.

Below are some photos of a fully tanned fifth instar larva shot in various perspectives. Coloration is as follows: pale yellow-green body; shiny bright yellow head capsule, thoracic legs, prolegs, and posterior end; tubercles shiny blue at base, though dorsal set tipped with yellow while dorsal-lateral and lateral sets tipped with white; black spiracular rings; reddish black crochets and mandibles. The cuticle is loose, shiny, and faintly granulose. There is setae on the head capsule, thoracic legs, prolegs and tubercules. Body length 3 cm; head capsule width 4 mm; mass 0.9 g.

Here is a comparison between a freshly molted fifth instar and a full grown fourth instar. They are about the size, with the fourth instar being slightly larger if anything, though the anatomical proportions (head capsule and tubercle size to body size ratio, etc.)  are slightly different of course. The fifth instar has much more vibrant colors and is shinier since the white powder that had accumulated during the fourth instar was shed off when it molted.

Fully tanned fifth instar larva on citrus.

- Alan