Searching for Birthwort with the Spanish Festoon Butterfly

Searching for Birthwort with the Spanish Festoon Butterfly

Spanish Festoon (Photo: Steve Andrews)

The Spanish Festoon (Zerynthia rumina) is a very pretty butterfly in the Papilionidae or Swallowtail butterfly family. It has strikingly patterned wings of yellow, red and dark brown with zig-zag markings on its hindwings. It is found in Spain, Portugal, North Africa and southern France. I have seen the butterflies in scrubland and pine and oak forest near where I live, but until today I have never seen any of the Birthwort species (Aristolochia spp) this butterfly uses as food-plants for their caterpillars.

I have lived in Quinta do Conde in Portugal for the last five years but have never managed to find any type of Birthwort growing here so it has been a real mystery for me, as to how these butterflies survive here. Today after a lot of searching, I discovered a clump of Round-leaved Birthwort (A. rotunda) growing amongst trees and heather at the top of a bank.

Spanish Festoon habitat (Photo: Steve Andrews)

I had to climb up to find it, and this is why I had never seen it before, although I often walk through this part of the woodland. A female Spanish Festoon has to find this plant or other Birthwort species on which to lay her eggs. There are no other options. The distribution of the food-plants, as is the case with most butterflies and moths, is one of the main factors responsible for the distribution of these insects. In fact, if you find a colony of a particular butterfly or moth, you can be fairly certain that the plants the larvae of that specific species need will be growing nearby. 

Round-leaved Birthwort (Photo: Steve Andrews)

The Spanish Festoon is flying very early this year. Most sources say that it can be seen from April onward, although the excellent Collins Butterfly Guide, which says this butterfly flies from late March to May, also points out that it has been recorded in February. With the Climate Crisis making the weather a lot warmer, and leading to droughts and the very real danger of forest fires in Portugal, butterflies and other species of flora and fauna are directly affected by changes in the weather. 

The Birthwort species are poisonous plants that are dangerous for humans to consume, because poisoning from these plants can lead to kidney failure. These plants were once used to cause uterine contractions, hence the name “birthwort,” but their usage as a medicinal herb has mainly been abandoned due to the dangers of the toxins these plants contain. For the caterpillars of the Spanish Festoon, as is the case with the larvae of many butterflies that have poisonous food-plants, the poisons in the plant become a form of defence for the caterpillars. Because they become toxic too, any predators that try eating them are likely to get very sick. The European Birthwort (A. clematitis) is the species I was expecting to find, so I was pleasantly surprised to find the Round-leaved Birthwort was the local species. Birthworts tend to be straggling plants that need other vegetation or support to climb over. The Aristolochia species have unusual tube-shaped or pipe-shaped flowers, and one species, the Dutchman’s Pipe, which has very large and attractive blooms, is grown for ornamental purposes.