Pipevine Swallowtail Eggs are Just Starting to Come In

Today we found pipevine swallowtail (Battus philenor hirsuta) eggs for the first time this year.

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It is ironic that the one pipevine (Aristolochia californica) site that we frequent that we have never actually once witnessed a pipevine swallowtail (Battus philenor hirsuta) this or any other year was the one site that we finally found their eggs today, making the first eggs of the year.

Albany Hill has a large stand of pipevine growing along Cerrito Creek in a somewhat hidden location partially covered by other plants. But this is just the kind of place the stuff likes to grow and boy, this stand of pipevine is incredible both in size and vigor. We only discovered it this year, but like noted above, we've never actually seen any pipevine swallowtail flying around the hill or anywhere in Albany. While we don't doubt at all the ability of the relatively long-lived and strong flying swallowtails to find and locate their only host plant even when it's in the shade, it still came as a little surprise when we found two clusters of eggs there after not checking for several weeks. The first cluster, located on a new shoot (not particularly significant to note here since the entire vine is covered in new shoots) near the top of the vine and consisted of 17 eggs (unfortunately, a few were rubbed off and lost on the way back because we didn't have anything to hold the cutting with the eggs with). The second cluster was laid on the underside of a not so attractive leaf which also located very high up. There are 14 eggs in this cluster, but 9 of them appear to have had their insides sucked out, probably by some kind of true bug (Hemiptera).

I say that this find was ironic because we have been visiting our other local pipevine sites routinely for the past six weeks. Specifically, we have been taking scheduled two week interval trips to Tilden Regional Park and its botanical garden (Berkeley, CA) and visited Canyon Trail Park (El Cerrito, CA) a few weeks ago to no avail. Many times, we even witnessed the butterflies flying in the places near the pipevine (though they appeared to be mostly males). At the same time, our own pipevine swallowtails have basically all emerged sometime this month from diapausing chrysalises from last year. It was quite obvious that their spring flight had already initiated, but for some reason there were no eggs at all. Perhaps the females had not yet had quite enough time there to mate and get themselves ready to start spilling their eggs in big enough numbers for us to discover. And perhaps coincidentally, it is a bit strange that the pipevine growing at Albany Hill is also far ahead of those at other sites in terms of spring growth (they must have broken dormancy much earlier) and so happened to receive the first eggs of the season.  

Anyway, tomorrow we are going to take a look at the other sites and see if we have any luck now. It is almost May, so by now we are certain that it isn't too early. 

Authors
Brian Liang

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