Found a Pipevine Swallowtail Laying Eggs

Today we witnessed a pipevine swallowtail (Battus philenor hirsuta) laying an egg cluster on California pipevine (Aristolochia californica) at Albany Hill (Albany, California).

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It really takes a person to go checking every day in order to see a moment like this. Today, we were lucky enough to witness a female pipevine swallowtail (Battus philenor hirsuta) choosing a spot on the ground and laying eggs on a small, growing shoot of California pipevine (Aristolochia californica).

​We had seen the butterfly nectaring when we first got to Albany Hill, which was an interesting sight.​ We instantly recognized her as a female by the drab coloration on the front side of the forewings. 

About an hour later, she was still flying about around the pipevine. It was obvious that she was laying or intending on laying eggs there, and eventually she landed on the ground and waited for several minutes, touching the vine and twitching the ovipositor. Most females will spend hours investigating different shoots, landing on them but then leaving, but it appeared like she had for-sure chosen the right spot here. After a while, she very quickly laid a set of eight eggs over the course of about two minutes. The entire time she sat there, not flying out after each egg or really flapping the wings. 

The freshly laid eggs are interesting. After collecting so many egg clusters, we have never actually seen how they look like immediately after being deposited. The eggs look slightly wet and smooth because the grainy substance coating them hadn't dried yet. These particular eggs were also very orange and pale rather than bright red, possibly because the coat that gives them the red color was not dried or due to variation caused by genetics because we saw another cluster, discovered yesterday, that was orange but appeared to be dried. We also speculated that older females have less of the red substance and laid smaller clusters such as this one. 

​After we looked around, we discovered many egg clusters and groups of young first or second instar larvae that we hadn't before because they were all located so close to the ground. Last year during June, we also recall finding most of our eggs near the ground in the Berkeley Hills. It is likely that this is a common trend for the later season flights because this is where many of the new shoots/plants, now an extremely scarce resource, are located. 

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Authors
Brian Liang

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