Found Another Promethea Cocoon

We found a promethea moth (Callosamia promethea) cocoon on spicebush (Lindera benzoin) at Mundy Wildflower Garden in Ithaca, New York.​

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Today is the first day that it truly feels like Spring.

For the first time in months, the weather is sunny and in the mid 70's, which is a huge turnaround considering that it snowed here just last week (hopefully, for the last time this season!). We decided to take this amazing opportunity to take a walk around some of the old insect collecting sites on North Campus that we used to visit a lot when we first came to Ithaca last fall like the Cornell botanic garden, and Mundy Wildflower to take a look at where the ecosystem is at. 

For a few weeks now, we have been noticing lots of plants starting to grow out their branches and/or flower buds, although few have actually leafed yet.  We did notice a few bees, which overwinter as adults, around for the first time this year. We also saw a mourning cloak (Nymphalis antiopa), which is typically the first lep of the season since they too overwinter as adults. 

The last time we visited Mundy was last December, right before we left for winter break. Back then, all of the leaves had fallen on the spicebush trees (Lindera benzoin), making it easy to find any cocoons still attached. We had found a promethea moth (Callosamia promethea) cocoon then on one of the same trees that we had found them earlier that year. Presently, since the leaves are not grown in yet, we checked these hotspot trees again on our trip today and were thoroughly surprised to find another cocoon. This time of year should be when the spatial density of cocoons should be at its lowest due to mortality factors over the overwintering period. Moreover, it is surprising that we cold have missed this cocoon during our previous searches, such as the one in December. Interestingly, on the same tree, we found what appeared to the silken stalk of a promethea cocoon attached to a silken matted leaf, but with no cocoon. It must have somehow fallen off at some point.

After taking the cocoon that we found home, we weighed it with the twig still attached. Using a rough estimate for the twig weight, the tared weight should be around <2 grams. This seems quite light for a cocoon of decent size, but a steep drop in weight is routine after the overwintering period as the cocoon weathers and pupal water weight is lost through respiration. That is to say, we do still believe that the pupa is alive. It is unfortunate that the ~5 cocoons that we collected last year are no longer with us (we left the in our dorm refrigerator over winter break only to find that they had disappeared when we returned) or else there would be a very high chance that we would be able to obtain some sort of pairing. Now, with only this one cocoon, we will first need to hope that it is female and then find some way to call in a wild male. The good thing is, if it does turn out to be female, it should probably emerge at around the right time since it has been exposed to natural environmental conditions to this point. Indeed, given the warmth of today, we would not be surprised if it (and other local wild pupae) broke diapause by itself without the influence of indoor temperatures.  

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Brian Liang
Brian Liang is a student at Cornell University in Ithaca, New York pursuing an undergraduate degree in entomology. He is co-owner and a main contributor of the Liang Insects blog, insects articles, and site design. ​​

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