Assessing year-round phenology and reproduction of the migratory painted lady butterfly, Vanessa cardui (Lepidoptera: Nymphalidae), in a Mediterranean area in southern Spain

Mariano Cuadrado

doi:10.14411/eje.2021.029

Abstract

The painted lady, Vanessa cardui (Linnaeus, 1758), migrates seasonally between Africa and Europe with a northward multigenerational migration from Africa to Europe in spring and a southward migration from Europe to Africa in autumn. However, little is known about the year-round phenology of this species in southern regions in the Mediterranean Basin. In this study the year-round phenology and reproduction of painted ladies was recorded during a seven-year period (2014-2020) at 7 lowland sites (< 80 m a.s.l) near the coast of CĂĄdiz (southern Spain). Overall, a total of 2341 painted lady butterflies (or 0.56 butterflies/km) were recorded along 4186 km of transects of the Butterfly Monitoring Scheme (BMS). Data pooled for all sites and years indicate a migration of painted ladies in autumn (mid and late October), another peak in abundance in winter (late February) and finally a migration in spring (late May). Abundance, however, varied greatly between sites and years. In July 2019, a spectacular migration of painted ladies was recorded across the study area that was also recorded in other European countries a few weeks later. Territorial behaviour of males, including hill-topping and courtship, oviposition and immature stages were recorded in autumn and winter. Reproductive behaviour was not recorded in spring or summer. Painted ladies were most abundant during the autumn migration, less abundant in spring and much less abundant in winter. This study confirms that the southern tip of Western Europe close to North Africa is an important stop-over region during the migration of painted ladies although numbers fluctuate enormously between years and sites. To my knowledge, this is the first time that the timing of year-round migration and the reproduction of painted ladies in the autumn-winter months have been described for a southern European population.

Highlights

Every year, large numbers of many species of butterflies undertake seasonal movements that are considered to be true migrations (Williams, 1930, 1957)
Our results show that painted ladies (1) were more abundant in February, July and October; (2) were absent during spring (April–June 2019); (3) the number of butterflies and their abundance were exceptionally high (1,245 butterflies in 690.3 km, or 1.8 butterflies/km); (4) most of these butterflies were recorded between July 1 and 13, 2019 (977 butterflies in 51.4 km, or 19 butterflies/km) and (5) the abundance was remarkably high along some transects (e.g. 100.5 on 1-VII-19 and 57.3 on 3-VII19, both at Punta del Boquerón, 32.6 on 1-VII-19 at Camposoto or 7.5 on 5-VII-19 at Econatura)
According to information published by the press, the same phenomena was reported at other sites in Spain and was subsequently recorded in other European countries a few weeks later

Summary

Introduction

Large numbers of many species of butterflies undertake seasonal movements that are considered to be true migrations (Williams, 1930, 1957). The painted lady, Vanessa cardui, is a well-known butterfly with a worldwide distribution (for an overview, see Opler & Krizek, 1984; Bitzer, 2016) and multigenerational long-distance migrations. In the Palearctic, large numbers of painted ladies undertake seasonal movements between Africa and Europe, with a northward migration from Africa to Europe in spring and a southward migration from. Between 6–10 different generations are thought to be involved in an annual migratory loop of about 12,000–14,000 km between tropical West Africa and Scandinavia, which is the longest regular insect migration circuit currently known (Stefanescu et al, 2013; Menchetti et al, 2019; Hu et al, 2021)

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