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JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



Another dominant genus resembles the present-day Chalcidid Tory- 

 mus very closely, but on account of a somewhat less specialized wing- 

 venation, I have termed it Palaeotorymns. There are at least four dis- 

 tinct species from Florissant, represented by many specimens in the 

 collection. Because of its evident antiquity it has had ample chance 

 to give rise to variations in habits, through mutation or otherwise, and 

 we find that the present species of Torymus are parasites of gall in- 

 sects belonging to both the Diptera and Hymenoptera, and apparently 

 of certain Coleoptera and Lepidoptera as well. 



Chalets (including Smicra, Spiloclialcis, etc.) is another genus 

 that is well represented at Florissant, and recent species of this domi- 

 nant group attack insects belonging to at least three orders, Lepidop- 

 tera, Coleoptera, and Diptera. 



That very persistent types are not always the ones to give rise to 

 variations in habits is sho^vn by the occurrence of many species of 

 Limneria, Iclmeumon, Microgaster, Proctotrypes, etc., in these same 

 Miocene deposits. None of these particular genera seem to have at 

 present a wide range of hosts. 



Correlation between very slight characters and certain host relations 

 is very common, and I shall mention one in closing. The genus Tele- 

 nomus contains nearly 175 species of egg-parasites, and is distin- 

 guished from the closely allied Phanurus by such evanescent charac- 

 ters that many systematists recognize no generic division. Of the en- 

 tire series only two are known to breed in the eggs of Diptera. Botk 

 attack the eggs of Tdbanus, one in Europe and the other in America, 

 while taxonomically they exhibit particularly well the slight differen- 

 tial characters of Phanurus, although they cannot satisfactorily be se- 

 gregated from the rest of the genus upon a strictly morphological 



basis. 



To judge, then, from the fragmentary evidence so far adduced, we 

 can only suggest that the single explanation which seems applicable to 

 the constancy of some groups and the variability of others, lies in the 

 assumption of a general evolutionary trend toward gradual elabora- 

 tion, broken here and there by a mutation in habits which has split off" 

 the progenitors of certain groups from the conservative majority. The 

 fact that parasitism has undoubtedly originated independently in a 

 number of groups further enlarges the possibilities of complexity in 

 host relations. 



A paper was presented as follows : 



