PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



SMITHSONIAN INSTITUTION 



U. S. NATIONAL MUSEUM 



Vol. 93 Washington : 1943 No. 3170 



THE NORTH AMERICAN PARASITIC WASPS OF THE 

 GENUS TETRASTICHUS— A CONTRIBUTION TO BIO- 

 LOGICAL CONTROL OF INSECT PESTS 



By B. D. Burks* 



The genus Tetrastichus Haliday (Hymenoptera : Eulophidae) in- 

 cludes a large number of species of minute chalcid-flies. These may 

 be either primary parasites or hyperparasites, and they attack a wide 

 variety of hosts (see host list hereinafter), including such destructive 

 pests ib the Hessian fly and the cotton boll weevil and many kinds of 

 fchrips, aphids, midges, leaf miners, scales, tent caterpillars, borers, 

 roaches, beetles, and gall-makers injurious to agriculture, horticulture, 

 and forestry. The}* have been reared from the eggs, larvae, and 

 pupae of other insects, as well as from many plant galls. Economi- 

 cally, therefore, this is an important group of the Chaleidoidea, and 

 a thorough understanding of its species and relationships is desirable. 

 Twenty-three species are herein described for the first time. 



From a taxonomic standpoint this genus is a difficult one for 

 several reasons. The species are so small that very good microscope 

 equipment is needed for studying them. Specimens are only lightly 

 sclerotized, so that they almost invariably shrivel badly in drying; 

 this tends to conceal or distort their morphological characters. It 

 has not, however, been possible satisfactorily to study specimens pre- 

 served in alcohol or on slides. There is, furthermore, a great lack of 

 good, definite morphological characters for the separation of species 



♦Acknowledgment is made to the Illinois State Natural History Survey, Urbana, 111., 

 for granting the author a leave of absence on two occasions, which permitted him to accept 

 a temporary appointment by the U. S. Bureau of Entomology and Plant Quarantine, during 

 which period the work on this paper was done. 



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