EXTENT OF GIPSY-MOTH PARASITISM ABROAD. 129 



accomplished fact, although of course there is no assurance that it is 

 continuous and perfect. 



The final outcome of the Russian experience was, therefore, the 

 opposite of what might have been expected, and it resulted in a firmer 

 determination than ever to carry the work through to its end. 



PARASITISM OF THE GIPSY MOTH IN SOUTHERN FRANCE. 



Following the 10 days in Russia a shorter period was spent by the 

 junior author in somewhat similar field work in southern France, 

 where, with the aid of M. Dillon, he was enabled to visit the localities 

 from which the largest, and in that respect the most satisfactory, 

 shipments of parasite material ever received at the laboratory were 

 collected. As the direct result of the senior author's visit to Europe 

 in 1909 some thousands of boxes containing hundreds of thousands of 

 gipsy-moth caterpillars had been collected in the vicinity of Hyeres, 

 about 50 miles to the eastward of Marseilles. These caterpillars were 

 largely living upon receipt, and in the winter of 1909-10 Mr. W. B. 

 Thompson dissected several hundred preserved specimens and the 

 actual percentage of parasitism was thus determined. Some few pupae 

 which had also been received from the same locality made possible a 

 fair understanding of the extent to which the pupae were parasitized. 



The results of these investigations, taken in connection with the 

 actual rearing work, were disappointing. It was evident that the 

 moth was fairly common in the region from which the material was 

 collected — as common, perhaps, as it would need to be in Massachu- 

 setts to provide for an increase of sixfold annually. Nevertheless, 

 the amount of parasitism which was indicated by this, the most 

 thorough study of parasitism of the gipsy moth abroad which was 

 ever undertaken in the laboratory, was less than enough to offset a 

 twofold, much less a sixfold, increase. 



For this reason much curiosity was felt as to the conditions which 

 prevailed in a country where parasitism of such comparatively insig- 

 nificant proportions was sufficient. 



No sooner was the character of the country districts in this portion 

 of France seen than the wonder which had been felt at the small per- 

 centage of parasitism which was sufficient to hold it in check was 

 replaced by a much greater astonishment that the gipsy moth should 

 exist under such conditions at all. It was a country of olive orchards 

 and vineyards, with a strip along the littoral which was so nearly 

 frostless as to permit the culture of citrus fruits, and even of date 

 palms. The hills were semiarid, with the soil exceedingly scanty and 

 often covered by loose stones. The principal forests consisted largely 

 of cork oak and pine, except in the low and well-watered valleys and 

 bottom lands where other trees in considerable variety occurred. 

 95677°— Bull. 91—11 9 



