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A FILM OF PARASITOLOGY
Rather than an agricultural film, the picture made by Professor Omegna at the request of the National Institute L. U. C. E. of Rome, might be defined as a film of agricultural defence.
The film shows the peculiarities of the olive fly [Dacus Oleae Rossi), and the possibilities of combatting it in the interest of the cultivation of the olive.
The Dacus Oleae Rossi is similar in form to the ordinary housefly, but much smaller; being barely 5 mill, long and of a greenish yellow colour. The fully grown fly prefers sugary substances for its nourishment and when these are not available, it feeds on the liquid which it extracts from the olive by piercing it.
The females, fecundated 3 or 6 days after their mating, breed on the olive tree, piercing its fruit and forming for themselves by means of movements from right to left, a small habitation, where they place their eggs. The greatest danger to agriculture is constituted by the large number of eggs (up to 1000 for each female), that may be deposited.
The larvae which emerge after a few days, hollow out a small tunnel inside the olive, which is gradually enlarged as the larva grows and presses forward. In summer, after 12 or 13 days, the completely formed larva penetrates towards the epider
mis of the olive, where it hollows out a circular zone, entirely consuming the pulp and leaving only the epidermis intact, after which it isolates itself in a small compartment, where it transforms itself into a chrysalis, and does not emerge again until it has become a fully formed insect.
The struggle against this insect is carried on in Italy by four kinds of parasites with habits almost identical with those of the olive fly, and which lay their eggs in the same holes made in the olives by their predecessors. A thorough-going parasite that lives exclusively at the expense of the fly is the Opius Africanus Syepl, a native of Liberia, and other African zones. In the struggle between the two larvae it is always the parasite that wins and that therefore, although slowly, brings about a gradual liberation from the olive fly of the infected zones.
The film edited by the L. U. C. E. is of eminent practical value. By means of this picture and others which are being popularised in the field of parasitology, the Institute is attempting to spread among agriculturists the principles that must govern agricultural life, and to pass on the precepts of science to all those to whom they may bring the means of life and conquest.