Taking a Second Shot at Eastern Tiger Swallowtail Ovipositing

Now that we have two more gravid female Eastern Tiger Swallowtails (Papilio glaucus), we will attempt once again to have them lay eggs, this time in our new (and hopefully improved) ovipositing set up.

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We first obtained a fertilized female Eastern Tiger Swallowtail (Papilio glaucus) on 8/15 but didn't quite manage to squeeze any eggs out of it in our ovipositing enclosure in the day or two before it got away. Unlike our Anise Swallowtails (Papilio zelicaon) and presumably other machaon group swallowtails, glaucus group swallowtails are known not to start laying until at least a few days after mating so that might have been the problem.

Other than that, the issue lies mainly in the set up. There are two basic approaches one can take in setting up an ovipositing enclosure for these types of butterflies: (1) mimicking the natural environment of the species by creating a large enough space to allow it fly around while also providing natural nectar sources or (2) confining it to the smallest space possible such that it can still move about and lay eggs but maximizes the chance of contact between the host plant which stimulates oviposition. Our first attempt used the second method; we confined out gravid female into a very small 12 x 12 x 24 laundry bag with a small branch of host plant American plum (Prunus americana) stuck in a cup of water. Strangely, the female couldn't fly very well anyway. 

Today, with two gravid females -- one a reasonably sized black form female and the other a small yellow form female -- we decided that we needed to set up a new, hopefully improved, enclosure. It had already been two days since the black one was mated and one day since the yellow one was so it probably couldn't hurt to start today. We fed them well with sugar water, every day that they were alive and at least the black one is getting quite bulky.

Since both of these females seemed to have no trouble flying, we took the first approach for our new set up. We borrowed the 24 x 24 x 36 inch mesh screening cage that we keep katydids in and cut two huge branches of plum. We stuck the branches in a jar of water and put the jar on top of an upside-down pot to elevate such that the branches would hit the top of the enclosure which is where the butterflies like to hang out. It is certainly roomy enough for them to fly freely with literally being forced onto the plant.  

By the time we got the butterflies in the enclosure, it was already 3 PM and wasn't very sunny (63 degrees and partly cloudy today) so they just roosted for the rest of the day. But hopefully, within a few days, we shall see if this method proves effective. The only other issue that we might be able to fix with this set up is the host plant. While any suitable ovipositing host of this polyphagous species should be fine, the females still has strong preferences for certain hosts, often regional. Some members of the magnolia family (Magnoliaceae) seem to be strong contenders and are used almost exclusively in the southern range; however, we obtained these from an Ohio breeder where Prunus is more frequently used. No matter what regional host, it is difficult with polyphagous feeders because they usually don't rely nearly as heavily on host plant allelochemicals as monophagous species; therefore, the females probably won't have nearly as strong of a reaction to the host plant simply by making contact with it and detecting the chemical makeup in the leaves. If this all doesn't work, we have few chances left, at least this year, since we only have three remaining chrysalises that look like they could all be females (not good since our males will surely be dead by then [three of five already are]). 

- Brian