Pipevine Swallowtail Caterpillars and More Eggs

5/1/2017

We returned to Tilden Regional Park (Berkeley, CA) today and found more pipevine swallowtail (Battus philenor hirsuta) eggs as well as some young caterpillars.

Just yesterday when we went to Tilden, we found an insane amount of pipevine swallowtail (Battus philenor hirsuta) eggs (172 over 10 ten clusters to be exact) and observed dozens of butterflies--both males and gravid females--after only a short search so we anticipated that we would be able to find a hefty amount more if we returned today. Checking areas on the pipevine (Aristolochia californica) that we hadn't previously checked very well, we quickly managed to find a handful more egg clusters.

But what really surprised us was when we started checking some of the very small, isolated plants growing in full sun away from the main stand. These plants weren't doing particularly well in the full sunshine (it was very hot), especially since the vine is a riparian shade plant, but for some reason the female pipevine swallowtails must have loved them because we were finding young larvae left and right only on these! Truly, almost every little plant seemed to have a few caterpillars on them, ranging from mature first instars to third instars, and there were also a number of egg clusters too. As host plant specialists and vine (not tree) feeders, these caterpillars have a very fast growth rate (especially with the heat we have been seeing this past week) so we suspected that they were either not here or still eggs during the last time we had come which is why we probably missed them despite probably briefly looking at these plants then as well.

In total, we counted over 70 individuals. As for eggs, we found a total of 10 egg clusters again but the total was only 159. The clusters this time were generally smaller than yesterday's with the largest cluster being 23 (yesterday's largest were 27 and 24). The grand total is now 353 eggs over 22 clusters for an average clutch size of about 16 eggs which is quite large.

Authors
Brian Liang

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