Eri Silkmoth Second Brood Begins - Now to Find Host Plant

The eggs laid by the Eri Silkmoths (Samia ricini) we reared in September-October have begun hatching, beginning our second brood of this species this year. We now face the challenge of finding a suitable host plant during this season to rear them on. 

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​After a long fifteen days, eleven of the 200+ unsterilized eggs laid by the second eclosed Eri Silkmoth hatched today.

This hatching marks the beginning of our second brood of S. ricini this year and conditions couldn't be less ideal. We have way more eggs than we can possibly handle (~1000), the weather is a bit too cold and humid, and finding enough host plants is a serious challenge. However, we are still going to try our best and pull this brood through the winter so that we can continue this species line. The non-ideal winter weather will cause slower growth, but that's fine as long as they survive. We are mainly concerned with finding host plants, since there have never been local sources of Castor Bean (Ricinis) or Ailanthus (Ailanthus). Further, the commonly used alternative Ligustrum is very limited to us, and Prunus which we used the first time around has almost completely senesced. So, we are completely out of options except experiment with evergreen plants around our neighborhood to see what they we accept.

After searching everywhere for evergreen plants that we thought looked reasonably "edible", we transferred the neonate larvae into a petri dish and begin putting in various leaves. First, we stuck in some ornamental rose (Rosa) that is sometimes reported as an accepted alternative, though it is not very abundant since it is a bush, not a tree. Then we added some citrus (Citrus) since some members of other Attacine genera such as Rothschildia, Attacus, and Epiphora will accept related Rutaceae plants, and it is extremely common around here. We also added some ceanothus (Ceanothus) because most members of the Attacine genera Epiphora and Hyalophora accept it. Next was elderberry (Sambucus) for no particular reason except that the leaves still look healthy, and last was an unidentified evergreen Lauraceae tree that is quite common around here that we've been wanting to identify and make use of for quite some time. There were also several other random evergreen plants we could've added such as camellia (Camellia), another unidentified Lauraceae, coast live oak (Quercus), etc., but we thought five hosts was already enough to test for now.

Soon after adding new different hosts, we immediately witnessed one of the neonate larva initiate feeding on the unidentified Lauraceae which really took us by surprise, since it was just a random tree that we couldn't even identify. A few minutes later, a different one took a nibble out of the rose which we were hoping for since it has been reported as a suitable host by some. A while later, one of them seemed to be biting at the cut stem end of the ceanothus, though we're not completely sure. Finally, one of them took a pretty large bite out of the citrus which we were quite excited about since this is the one host that is very abundant here and grows in this season. None initiated feeding on the elderberry, though interestingly, several of them have crawled on it and are staying contently. So far, we do not know if any of the larvae that began feeding on one of the hosts will actually continue to feed on it and develop healthily, but at least they started. When more caterpillars hatch tomorrow we will definitely experiment more with host plants and hopefully it will be more clear which hosts they will accept with a larger sample size. ​

- Alan