Thistle butterfly or colorful butterfly(Vanessa cardui L. Lepidoptera: Nymphalidae) competitor for bees in beekeeping areas?

The population of Vanessa cardui has increased in some years due to rising rainfall and vegetation, and is abundantly seen in gardens and farms in the flowers, that cause problems for beekeepers and farmers. Late in winter of 2018 and spring 2019, the population of V. cardui increased in some area and made problems for beekeepers due to over population and feeding of mature butterflies from the nectar of the plants, were as a rival against honeybees.Thistle butterflies are dependent on tropical and temperate habitats to complete their life cycle. The growth and length of each generation in tropical and semi-tropical areas is 33 to 44 days and in the temperate and cold areas is 60 days or more. Mature butterflies are alive after emerging from pupa, for 10 to 24 days but in general, durability of them in the generation of egg to death is about one year. Each female butterfly lay about 500 eggs. They are able to create several generations during migration. V. cardui has a wild dispersion in the world and distributed in the Asia, Europe, Africa, America and Australia but not reported in southern Australia and Antarctica. Therefore, thistle butterfly is a cosmopolitan butterfly. Thistle butterfly was reported also from most provinces of Iran. In the spring of 1992, over population of thistle butterfly and more than that in spring 2019, caused damage to the beekeepers. Of course, in 1992, the major population of V. cardui were in south of the country and rarely in the north and temperate regions. But, in 2019, they migrated to the northern areas of the country and cause worried for farmers and beekeepers. V. cardui has long migration. Two immigration paths of this species have well studied between North Africa and Europe, and also between South and North America. Colorful butterflies during this migration are traveled over 15000 kilometers. Immigration of V. cardui from North Africa to northeast Spain is going to be with the help of wind, and atmospheric phenomena plays an important role in their migration. V. cardui feed on more than 100 plants such as goats-rue, clover, bugloss, salvia, self-heal, thyme, stonecrop, centaury, syrian thistle, cotton thistle and yarrow.  When these butterfly are found abundantly, they are acting as a rival against honeybees and other pollinator insects in the use of nectar on the flowers of the plants. Generally, reduction of available nectar for honeybees, Increase the need to feed the colonies and consequently enhance cost of beekeeping. During this period, the pollen used by honeybees in this area is not invasion by butterfly. Despite the high rainfall in winter 2018 and early spring 2019, there was no acceptable production in honeybee colonies of most region in Alborz Mountains. So, beekeepers for sustainability of their colonies will continue to feed the colonies in the spring to compensate the deficiencies of the nectar because of invasion of V. cardui in the region. This situation had less intensity in the western parts of the country and Zagros Mountains, so honey production was more in apiaries of Zagros Mountains. It seems that, deploying honeybee colonies on far-flung routes of butterfly migration will reduce their negative impacts.