Eltham is a suburb within the Banyule city council and they have organised the event to count Eltham Copper Butterfly caterpillars. Each year these counts are carried out to assess population stability at each of the butterfly colonies. With this information, they monitor changes in population size, host plant use and butterfly distribution over time. The Eltham copper is a threatened species of butterfly that is restricted to small populations in Eltham, Greensborough, Castlemaine, Bendigo and Kiata, in Victoria, Australia http://www.theage.com.au/news/national/back-from-the-brink/2008/01/22/1200764265940.html. It has only one host food plant, Bursaria spinosa (sweet Bursaria); and the caterpillars are attended by several species of Notoncus ant. The ants offer protection against predators and parasites, and in return, the caterpillars secrete a sweet, sugary secretion from an organ on its abdomen, which they offer as food to reward the ants. During this survey, the number of caterpillars per plant, and the height and location of plants were recorded.
The cream coloured caterpillars live in ant nests at the bottom of the bushes during the day. They come out of the nest during the night to feed on the leaves of the bush. Therefore the event started at 8 pm in the night (it was the end of Spring and sunset was around 7.30 pm). I took the train to Greensborough which is about 20 minutes journey from Fairfield where I live in Melbourne.
There were 12 volunteers including me. After a briefing of the methods, all 12 volunteers started walking slowly with their torches ready looking for sweet Bursaria plants. We actually had to look for the black Notoncus ants who are accompanying the caterpillars. It took around 30 minutes to record the first caterpillar surrounded by a group of ants and we all gathered around the plant to see them as some of us had never seen this caterpillar before. We all were thrilled as we gained some good results as the time passed. We counted around 30 caterpillars by the time I left the team at 10 pm. It was such a fascinating time which gave me great satisfaction though it was freezing cold.