The first adults to eclose (emerge from their pupa) in early spring are the males. Starting at around 5:30 p.m., hundreds of males fly vigorously and relentlessly in search for cocoons containing females about to eclose. They approach trees and move around them, zigzagging and crawling on branches. If they do not find females with whom they will have the chance to copulate, they fly off and continue their search. It has been suggested that male activity is dependent on temperature, since below 59 ˚F (15 ˚C) only a small number of males are found to be actively looking for females. It has also been reported that females emit a calling pheromone before they emerge from the pupae, causing an increase in male activity around the cocoon before they eclose. In addition, males have been seen approaching and moving around brown objects, suggesting that males also use visual cues to find females. Within one or two seconds after the tip of the female abdomen clears the cocoon, males begin copulation, which lasts an average of 202 minutes. In order to position himself, the male moves backwards and bends his abdomen towards the female, pushing the tip towards the female's bursa copulatrix. There is a significant positive correlation between the body sizes of copulating pairs, which indicates that mating is not random with respect to size, presumably because of male-male competition for larger females.