Thursday, May 2, 2019

Difficult Delivery

"Hey, a little privacy here!"
PVST egg cluster-day one - REK
I spotted this pipevine swallowtail (PVST) desperately hanging onto a vine in gusts of heavy wind.  She was flailing about while struggling to get the tip of her abdomen into contact with the vein of a leaf.  There were 7 eggs stacked on it and she was trying to glue on number 8.  I took this video of her struggles and the next morning I returned and found 12 eggs on the leaf and another 12 on the petiole of a nearby leaf.

Dutchman's pipe flower - A. tomentosa - REK
The pipevine swallowtail, Battus philenor, is a beautiful butterfly that can be easily confused with the other "black swallowtails," the spicebush ST, black ST and the occasional dark phase of the tiger ST.  As the name suggests, their obligate host plants are plants in the genus Aristolochia, or pipevines.  Our backyard plantings are woolly dutchman’s pipe, Aristolochia tomentosa.



Nutrition bumps - Donald Hall

This butterfly's desperate attempts to lay her eggs in a cluster is a biological trait for this species.  The caterpillars that emerge are gregarious early on, and will get their first meal from the egg shell which contains drops of hard nutritious secretions in rows on the outside of the shell.  The female produces these secretions from a large specialized gland that lies above her ovipositor duct, like delivering a baby with a bottle by its side.  Later instars will separate, avoiding competition for food sources.

First instar feast - Donald Hall, U Florida

Early instars - REK
Soon the young caterpillars spread out, hiding in the dense clusters of pipevine leaves.  The later instars develop orange bumps that may be an aposematic advertisement, warning potential predators to look elsewhere for a meal.  The Aristolochia host plants provide them with aristolochic acids which are distasteful and even toxic to some predators.


Final Instar - REK

How it all begins - Gala Keller


The University of Florida Creatures pages at http://entnemdept.ufl.edu/creatures/ are a fantastic resource for their Featured Creatures, and a special thanks to Donald Hall for letting me use his photographs.