U. S. D. A., B. E. Tech. Ser. 20, Pt. VI. P. 1. 1., February 10, 1913. 



TECHNICAL PAPERS ON MISCELLANEOUS 

 FOREST INSECTS. 



VI. CHALCIDIDS INJURIOUS TO FOREST-TREE SEEDS.' 



By S. A. RoHWER, 



Entomological Assistant. 



INTRODUCTION. 



For a long time entomologists were loath to give up the theory that 

 all chalcidids were parasitic, and most of the species which attacked 

 the seeds of forest trees were originally described as being parasitic 

 on some other insect which either lived within the seeds of the trees 

 or lived within the cones, but in 1893 Wachtl recorded definitely that 

 Megastigmus spermotrophus lives within the seeds of Douglas fir and 

 is phytophagous. Even after this statement entomologists were loath 

 to believe that any chalcidids are not parasitic, and many of the fore- 

 most authorities on these insects believed up to the time of their 

 death that some day it would be proven that all chalcidids, with 

 the exception of certain few belonging to the genus Isosoma and 

 its allies, are parasitic. Of late years, however, most entomologists 

 have come to believe that the phytophagous habit in many of the 

 chalcidids is not uncommon. We know at present phytophagous 

 species of the family Collimanidae (olim Torymidge), of the sub- 

 families CoUimaninse and Megastigminse, and of the family Eury- 

 tomidae, the phytophagous species being in the tribes Isosomini 

 and Eurytomini. To these also may be added certain genera which 

 have been assigned to the family PerUampidse. 



The species that attack seeds of forest trees are confined to the CoUi- 

 manidse, and most of them belong to the subfamily Megastigminse. 

 Summing up the literature on phytophagous Chalcidoidea belong- 

 ing to this family, it is possible to outline the life history of every 

 species which may live withm the seeds of forest trees. This would 

 be as follows: The egg is laid in the early summer or late spring, 



I Although certain hymenopterous insects belonging to the superfamily Chalcidoidea have been shown 

 to be very injiu-ious to the seeds of certain forest trees, very little work has been done on these insects in 

 America. The present paper is a r&ume of the literature which deals with these insects, with a bibliog- 

 raphy of the literature. It is prepared to facilitate the work of field men and to call the attention of ento- 

 mologists in general to the damage done by these insects. 



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