around eight days. The eggs are white and shaped like flattened spheres. The eggs are very small, about . The ground color of the egg sac is pale-greenish grey, with the actual arrangement being white. Eggs are laid singly on young shoots of the food plant. Larvae The larvae emerge around a week or two after eggs are laid. The larvae of P. icarus feed on the underside of leaves, causing blotching. Hibernation occurs as a half-grown larvae. They are attractive to ants of genera Myrmica, Lasius, Formica, Plagiolepiss, but not as much as some other species of blues. The chrysalis is olive green/brown and formed on the ground, where it is attended by ants of genera Myrmica, Lasius, Formica, Plagiolepiss, which will often take it into their nests. The larva creates a substance called honeydew, which the ants eat while the butterfly lives in the ant hill. The relationship between these ants and blue common larvae is described to be facultatively mutualistic. Instars of larvae There are five instars of larvae. During the first instar, larva emerge and eat away the crown of the egg. The segments of the larvae are large and rounded, and the following segments are smaller. The body is a light green, and is whitish in light. This stage lasts about nine days. The second instar, after the first moult, adds a couple of body segments onto the larvae, and the body is more green. The third instar signifies more feeding and growing in size of the larvae. They are about long and the head and legs are black colored. In the fourth and fifth instar, the larvae becomes very green, has ten body segments, and measures about in length. External effects on larval growth and development Larval growth rates are thought to be determined mainly by temperature and food quality and availability. The larvae of P. icarus are oligophagous, meaning they utilize a range of host plants in the family fabaceae, as well as have a mutualistic relationship with ants. For both male and female larvae, the total development time is longer with longer day lengths, corresponding to earlier times in the season. When larvae are born earlier in the season, they take a longer time to develop. When they are born later, they take a shorter time to develop. Thus the external effect of photoperiod affects the length of development for the larvae.