As we were looking for Pipevine Swallowtails (Battus Philenor) at Tilden Regional Park, Berkeley, CA, we realized how critical it was for the species to have new pipevine (Aristolochia) shoots available to lay their eggs on and for the newborns to eat. It is probably a well-known fact that healthy, tender foliage is more attractive to most adult Lepidoptera, particularly butterflies, and is more appealing for them to lay eggs on. Anybody who is willing to take the time to search for eggs or caterpillars will soon realize that one of the best strategies to maximize efficiency is to first look for them on younger plants or on the new growth. However, this preference for new growth varies from species to species and is slightly more complex then it seems when considering that most plants only exhibit new growth during a certain time of the year. In particular, Pipevine Swallowtail (Battus philenor) females are notoriously picky with the egg-laying sites, probably because it lays them in relatively large clusters as opposed to singly, and therefore must put extra care in ensuring that it does not jeopardize the future of a very large number of its offspring with one wrong move. Even more so with our "hairy" Californian subspecies hirsuta which is known to lay larger clusters of eggs, on average, than the species. The females may spend hours circling a potential egg-laying site before deciding on the best location to deposit her eggs. And the worst part is that she will only ever lay eggs of new shoots tips or leaves of their beloved Pipevine no matter how large or robust the vine itself may be or how risky it may be to the future of the species (We can testify to this as all 18 egg clusters we have encountered this year have been laid on new growth.). The dilemma here is that Pipevine, at least the single variety utilized in our region Aristolochia californica, only proliferates during the spring to early summer. Now, one would think that a simple solution to this would for the Pipevine Swallowtails to simply enter pupal diapause once new growth ceases in the summer months. But that is clearly not the case as they can actually be seen in flight well into the fall and continue to have many reproductive events months after new growth should have dissapeared. How is this possible? Well, to tell the truth, not all spring and early-summer generation pupa emerge to continue breeding; many of them do, in fact, enter diapause until the following spring where there is a massive flight. The choice to diapause and diapause length is seemingly random (not controlled by photoperiod as it is in many species) with some pupa emerging normally in two to three weeks after pupation, some emerging later in the season of the same year in a rather staggered fashion, and the rest diaupausing through the entire winter until the spring flight mentioned before. Through this strange regulation of the life cycle, the Pipevine Swallowtails can ensure that even if there happens not to be any new shoots on which to breed later in the season, the entire population doesn't simply collapse and that there will be at least some survivors of the generation that will breed next spring. Yes, it is pretty unstable, but it must work to some extent otherwise they would never have evolved to be like this and would probably be extinct by now. In addition, new Pipevine growth after early summer is not impossible. Like most plants, especially fast growing vines, Pipevine will regenerate itself rapidly should it be cut down or burned. Because this is so rare, any new growth during this time after early summer is likely to be utterly clobbered in eggs. In fact, unlike most species, Pipevine Swallowtails actually seemed to be encouraged to lay eggs where there are already rather then being deterred by the competition. So when we went down to Tilden Regional Park today, we brought a pair of scissors so that we could cut the old shoots off the Pipevines in order to stimulate regeneration. The pipevines there actually already have a reasonable amount of relatively new shoots because it is not especially late in the season (hence the fact that virtually of the egg clusters we have collected have been from here), but a little extra help for the butterflies couldn't hurt. On the other hand, the pipevine growing at Canyon Trail Park has not a trace of new growth; despite capturing a female butterfly there, we have yet to find a single cluster of eggs. The next time we visit, we are sure to also bring scissors and cut down every shoot we see. - Brian
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Timeline 2012–2017
Albany, California This timeline is a series of daily posts recording our observations on and experiences with various insects in Albany California and surrounding areas, from 2012-2017. Since we did not publish this site until 2016, posts before that were constructed retroactively. Starting in August 2017, we moved to Ithaca, New York; posts from there on can be viewed at Timeline 2017-present: Ithaca, New York. Archives (1,011)
August 2017 (49) July 2017 (121) June 2017 (79) May 2017 (77) April 2017 (91) March 2017 (35) February 2017 (12) January 2017 (10) December 2016 (12) November 2016 (26) October 2016 (49) September 2016 (84) August 2016 (94) July 2016 (99) June 2016 (53) May 2016 (21) April 2016 (4) January 2016 (1) August 2015 (3) July 2015 (3) June 2015 (2) June 2014 (3) May 2014 (1) April 2014 (3) March 2014 (3) December 2013 (2) November 2013 (2) October 2013 (5) September 2013 (11) August 2013 (15) July 2013 (9) June 2013 (5) May 2013 (4) April 2013 (3) March 2013 (2) February 2013 (3) January 2013 (2) December 2012 (2) November 2012 (1) October 2012 (2) September 2012 (2) August 2012 (5) July 2012 (1) June 2012 (1) Authors
![]() ![]() Full Species List (Alphabetical by scientific name) Note: - Not every species we encounter is necessarily presented on this site, rather a selection of those that were of particular interest to us and that we felt were worth documenting. - We can't guarantee that all species have been identified accurately, particularly taxa we are not as familiar with. Lepidoptera Actias luna Adelpha californica Agraulis vanillae Allancastria cerisyi Antheraea mylitta Antheraea polyphemus Anthocharis sara Argema mimosae Attacus atlas Battus philenor hirsuta Bombyx mori Caligo atreus Callosamia promethea Coenonympha tullia california Citheronia regalis Cricula trifenestrata Danaus plexippus Eacles imperialis Erynnis tristis Estigmene acrea Eumorpha achemon Eupackardia calleta Furcula cinereoides Heliconius erato Heliconius hecale Heliconius sapho Heliconius sara Hyalophora cecropia Hyalophora columbia Hyalophora euryalus Hylephila phyleus Hyles lineata Junonia coenia Langia zenzeroides formosana Lophocampa maculata Manduca sexta Morpho peleides Nymphalis antiopa Orgyia vetusta Orthosia hibisci quenquefasciata Pachysphinx modesta Papilio cresphontes Papilio eurymedon Papilio glaucus Papilio machaon oregonius Papilio multicaudata Papilio polyxenes asterius Papilio rumiko Papilio rutulus Papilio zelicaon Phyciodes mylitta Phyciodes pulchella Pieris rapae Plejebus acmon Poanes melane Polites sabuleti Polygonia satyrus Pyrgus communis Rothschildia jacobaeae Samia cynthia advena Samia ricini Smerinthus cerisyi Smerinthus ophthalmica Strymon melinus Trichoplusia ni Uresephita reversalis Vanessa annabella Vanessa atalanta Vanessa cardui Unidentified Lepidoptera Hybrids Papilio glaucus × Papilio rutulus Papilio polyxenes asterius × Papilio zelicaon Orthoptera Melanoplus devastator Phaneroptera nana Pristoceuthophilus pacificus Scudderia mexicana Trimerotropis pallidipennis Phasmatodea Carausius morosus Phyllium giganteum Mantodea Mantis religiosa Phyllocrania paradoxa Hymenoptera Apis mellifera Bombus vosnesenskii Brachymeria ovata Linepithema humile Pediobius sp. Polistes dominula Xylocopa varipuncta Unidentified Diptera Lucilia sericata Unidentified Hemiptera Brochymena sp. Leptoglossus sp. Nezara viridula Odonata Argia vivida Libellula croceipennis Coleoptera Coccinella septempunctata Cycloneda polita Diabrotica undecimpunctata Hippodamia convergens Araneae (Class: Arachnida) Araneus diadematus Phidippus johnsoni |