BUREAU OF ENTOMOLOGY. 517 



fold increase, which would have been considered satisfactory, there 

 seems good evidence that it increased fiftyfold and perhaps much 

 more. It has about equaled Calosoma in actual destruction of gipsy 

 moths this year, and in addition has destroyed an appreciable per- 

 centage of the brown-tail caterpillars, and it is now turning its atten- 

 tion to such native species as the fall webworm, the tussock moth, and 

 other fall-feeding caterpillars. Its increase has been accompanied 

 by a dispersion amounting to 10 or 12 miles in every direction as a 

 minimum aggregate during the four years since its first colonization. 



Still another example is the European Monodontomerus, the re- 

 covery of which over a large area was made the subject of especial 

 mention in the last report. This species has continued its satisfac- 

 tory rate of increase and phenomenal rate of dispersion tliroughout 

 the year. It is well over the border line in New Hampshire, and 

 appears to be extending its range about 10 miles each year, and to 

 be maintaining a twenty-five fold annual increase. 



It has been somewhat disheartening in the course of the study of 

 the progress of the parasites in the field to find that certain species 

 liberated under the most favorable conditions can not be recovered 

 the next year; and even in the case of two species, both colonized in 

 1908 and apparently established in 1909, no traces could be recovered 

 in 1910. But on the other hand another species (Zygobothria), col- 

 onized in 1907, was recovered in 1910, three years later, for the first 

 time — in small numbers, it is true, but over a considerable territory, 

 indicating a rapidity of dispersion suHicient to render a material 

 increase unnoticeable for the first two years. 



Another encouraging fact which may bo mentioned here is that an 

 important egg parasite {Anastatus hifasciatus) seemed this summer 

 to have demonstrated its ability to survive the New England winter, 

 and. having been colonized in 1909, appears to be strongly estab- 

 lished in 1910. 



On the whole,' the results of the work are distinctl}- more encourag- 

 ing than they have appeared to be heretofore, and we are by no means 

 disheartened over the nonrecovery during the present season of no 

 less than 15 species which have been colonized. In several instances 

 colonization has been much too recent to make their recovery probable, 

 on account of rapid dispersion ; and several others have never been re- 

 ceived in sufficient numbers to make a strong colony possible, so that 

 it may well be that establishment has not yet been accomplished. It 

 has been found in the course of this work that there is little hope of 

 the establishment of a colony of less than 1,000 individuals, and in 

 many instances, of course, it has been found impossible to put out so 

 large a number. 



The insight which is being gained at the laboratory into many 

 points connected with the biology of these important and interesting 

 insects is resulting, in practical knowledge that can not fail to be of 

 high importance in the continuation of the investigation. Some 

 changes in plans will be indicated in another part of this report. 



OTHER IMPORTATIONS OF USEFUL INSECTS. 



The greatly increased damage done in portions of Massachusetts by 

 the European leopard moth, an insect whose larva bores into the 

 limbs of many shade trees, and which at present is confined to eastern 



