BUTTERFLIES: THE REPRODUCTIVE STRATEGIES
In view of their dimensions, male and female insects have considerable difficulty in meeting and reproducing within the environment. For many of them obstacles that for us are insignificant become practically insurmountable. This is not the case for butterflies, who are equipped with good capacities for movement and, apart form the moths, also with excellent sight. The rule that holds for all male butterflies is to find a virgin female. Only thus will they have the best chance of reproductive success and hence of leaving their own genetic message to posterity. The moths, which fly by night, have resolved this problem through the emission, on the part of newly-emerged females, of sexual pheromones that attract the males even from a great distance. With butterflies, instead, the affair is more complex and each species features reproductive strategies that are different, even considerably so. Sometimes even within the same species we can find different approaches being used to trace and court the females. Among the principal reproductive strategies, we shall dwell here on some of the most significant examples of Italian and tropical species. Nevertheless, we have to add that finding a female is not the only problem the males have to tackle. In fact, they spend a lot of their time resolving territorial conflicts by means of air battles and ambushes, so as to display their strength and vigour in front of the females that make sure to flutter through the areas where the males gather.
WHAT A LIFE! FOR THE SMALL TORTOISESHELL
The males of this species perch at length on tufts of nettles. In fact the male knows that there, sooner or later, a young female will hatch. However, in the meantime, he has to defend his territory from intruders, which he chases in flights that have a striking resemblance to air battles. Effectively, the winner is the butterfly that manages to catch its enemy’s tail. However, if a female arrives in the meantime, she will not mate immediately, and the male has to take care not to lose sight of her, even when, in the evening, she goes to hide among the nettles. Only then, if he manages to follow her, will his long and patient labour be rewarded.
THE PATROL OF THE SCARCE SWALLOWTAIL
For this species defence of the territory consists in incessantly patrolling a vast area, which may even be several kilometres in length. The chosen sites are often hedgerows, rows of trees and all the areas where plants that caterpillars feed on grow – hawthorn and sloe bushes, for example – where it is more likely to find newly-hatched females. Anyone who happens to go walking through places frequented by the scarce swallowtails will have the impression of seeing many individuals of the same species, whereas often they are actually only one or two which, fluttering around continually on their patrols are constantly spotted in different places.
THE HILLTOPPING OF THE COMMON YELLOW SWALLOWTAIL
The males of the common yellow swallowtail recognise hilltops, treetops or other high spots as the arena for the ritualisation of their reproductive behaviour. At times, dozens of them gather on bare and barren hilltops, competing for the conquest of the highest perch. Their battles consist of rotating upward flights and in chasing off intruders. The females fly to such sites only rarely, and are immediately pursued by the most active males who then force them to land.
THE "PUPAL MATING" OF THE ZEBRA LONGWING
The males of the zebra longwing scour vast areas where passion flowers grow, a plant that is a favourite foodstuff of caterpillars, in search of female chrysalises. Once they have found them, then perch on top of them and then spread their wings seeking to prevent the approach of other males. However, they do not always succeed and it is not rare to see from two up to even four males hanging onto the chrysalis even for days at a time waiting for the females to hatch. Then, just a few hours before the female is ready to emerge, the male perforates the chrysalis and latches onto the immature female to mate.
