More Eri Caterpillar Host Plant Testing

We continue to search for a suitable host plant for our Eri caterpillars (Samia ricini). Due to a large hatching today, we should be able to get a more accurate idea of their preferences using a larger sample since. 

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Yesterday a few of our Eri caterpillars hatched and we offered a choice of five host plants in a petri dish: ornamental rose (Rosa), citrus (Citrus), ceanothus (Ceanothus), elderberry (Sambucus), and an unidentified tree in the laurel family (Lauraceae). When we checked on the larvae this afternoon, we were quite disappointed (and worried) to find that there was virtually no feeding on any of the host leaves, nor was there any frass. There were maybe a few minute sized holes on the citrus leaf and a hole on the rose and unidentified Lauraceae. Ceanothus and elderberry were completely untouched. However, the caterpillars were not wandering aimlessly around the dish as they would had if it were empty, but instead were all settled down on one of the host leaves. Several were on the citrus, and a few were on rose and the Lauraceae. This affinity towards the leaves is a hopeful sign that perhaps they may still be utilizable. So, since only the citrus, rose, and Lauraceae had caterpillars on them, we tossed out the ceanothus and elderberry and got some fresh leaves of the former three hosts.

As expected, there was a much larger hatching today (60+) of the unsterilized second eclosed female's eggs, so we merged these with the ones that hatched yesterday and divided them up onto the three hosts. This larger sample size should give us a more accurate idea of their preferences. We put 30 on the citrus since it seemed to be the most popular based on yesterday's hatchling's behavior (most holes and caterpillars on it), 25 on rose and 18 on the Lauraceae. Just like yesterday, immediately after placing the caterpillars on the hosts, several began nibbling at the edges but it was nothing extremely significant. We would need to wait until tomroow to see if they actually eat a decent portion of the leaf and leave frass. For now, the caterpillars seem quite content on the different hosts, especially the citrus, followed by the Lauraceae and the rose. Due to the larger numbers today, they have aggregated into large, tight groups on the underside of the leaves. Hopefully, by tomorrow at least one of the hosts will be eaten. 

- Alan