First Ceanothus Caterpillar Ecdyses into Fourth Instar

Our oldest third instar Ceanothus caterpillar (Hyalophora euryalus) has ecdysed into fourth instar.

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This afternoon at around 5:30 PM, the third instar Ceanothus caterpillar that entered apolysis on 7/5 began ecdysing into fourth instar and we took several time lapse photos as shown below with the time labeled.

Dorsal view:

Lateral view:

After ecdysing and tanning, a very apparent difference can be seen between the fourth and third instar. First, all the dorsal red tubercles have turned yellow and are more elongated but slimmer. They are also smoother, with only a few black spikes at the tip. The lateral blue tubercles are now paler and tipped with white. Also, there is now a black ring at the base of the six large yellow dorsal and middorsal tubercles on T2, T3, and A8 as well as on all the lateral blue tubercles. There is also now a white ring around the spircles. The body color is much more yellow green now rather than turquoise green. At around 9:00, the caterpillar began eating its exuviae, shown below.

On another note, it is interesting to compare how different the Ceanothus caterpillar's body shape and tubercles are from the Cecropia's caterpillars now. Below are pictures of the newly molted fourth instar Ceanothus caterpillar next to a newly molted fourth instar Cecropia caterpillar. The Ceanothus tubercles are much less pronounced and are rod-shaped, with a slight taper down the base. On the other hand, the Cecropia tubercles are much larger and more knob-shaped and are somewhat spherical at the top. The main difference in body shape is in the thorax between the two species. The Ceanothus thorax, when viewed laterally, is swollen and is bent at a defined angle at each of the large dorsal tubercles while the Cecropia thorax is a smooth curve. Also, the cross sections of the Ceanothus body in general are slightly angled at each tubercle (especially at the thorax), creating a very subtle octagonal prism body shape while the Cecropia is less so, having a more cylindrical body shape. Size-wise, the two species are still quite close, but the Ceanothus seems just slightly slimmer, though their head capsule are about the same size.

Also, since we are still struggling to deal with the disease, we decided the best option for us now is to purchase a live Ceanothus plant. Thus, we did so tonight and bought a decently sized Ceanothus griseus horizontalis plant. Once we make some small sleeves, we will put all the remaining healthy caterpillars on it and place the plant outside. Also, since we are unsure about pesticides, we placed the healthy second instar on it as a "lab rat" for now.

Today marks the end of third instar for the oldest caterpillar that lasted for approximately 8 days and 20 hours from 6/28-7/7. Second instar lasted for approximately 5 days and 8 hours from 6/23-6/28 and first instar for the oldest Ceanothus caterpillar lasted for approximately 5 days and 2 hours from 6/18-6/23. 

Count: L4: 1; L3+: 0; L3: 8; L2: 1; dead: 14 (1 missing, 12 disease, 1 squashed); suspected sick: 1

- Alan