Seasonal distribution and migrations of Agrotis ipsilon (Hufnagel) (Lepidoptera, Noctuidae)
Odiyo, P. Onyango
- Publisher: Centre for Overseas Pest Research (COPR)
The larva of the near-cosmopolitan noctuid moth Agrotis ipsi/on (Hufnagel) (-A. ypsilon, Rhyacia ypsi/on (Rott.), R. ypsilon (Warren), Scotia ipsilon (Rott.)) is popularly known as the greasy cutworm in Asia and North America, the dark sword grass in Britain, and the black cutworm in Europe. The name 'cutworm' reflects. its feeding habit of cutting off plant seedlings at the base of the stem, and the adjectives 'greasy' or 'black' describe its greasy, earthy-brown, blackish or grey-green appearance which is due to its black head, numerous dark tubercles, and dorsal longitudinal dark stripes and lateral pale ones. The greasy cutworm can be of very considerable economic importance, not only because of its prolific and often localized breeding but also because its nocturnal feeding habits often cause outbreaks to escape notice until a late stage. \ud \ud The sudden appearances of A. ipsilon, often in large numbers, and its seasonal disappearances, especially in India, the Celebes, Egypt and the Middle East, caused this pest to be recognized as a migrant about half a century ago. The present author has attempted to obtain additional circumstantial biogeographical evidence of major seasonal redistributions of populations on a world-wide basis, particularly over continental land masses and remote islands. This has been done by plotting historical records, obtained from museum specimens, light-traps and the scientific literature, on monthly distribution maps. This type of analysis has previously been undertaken for the armyworm moth, Spodoptera exempta (Walk.), in Africa (Betts, Haggis & Odiyo 1968), and for the Desert Locust, Schistocerca gregaria (Forsk.), throughout its vast distribution area in Africa, the Middle East and south-west Asia (Waloff 1946; Donnelly 1947; Davies 1952; Fortescue-Foulkes 1953). A further aim is to attempt an interpretation of the role of seasonal changes in the distribution of A. ipsilon as a natural means of adaptation.