DEXIDAE. 33 



are more nearly related to them. The following genera may be 

 taken for those which constitute the family: TRYPODERMA Wied. 

 (= Cuterebra Clark), CEPHALOMYIA Latr., CEPHENEMYIA Latr., 

 HYPODE-RMA Clark, GASTRUS Meig., AULACEPHALA Macq. and 

 CTENOSTYLUM Macq. A thorough limitation of these genera is 

 still wanted, and the name of Oestrus, instead of being dropped, as 

 we see it done by some authors, may perhaps be again restored to 

 its former rank. 



I have seen N. A. species of the genus TRYPODERMA, and others 

 of the genera CEPHALOMYIA and GASTRUS, introduced in America 

 from Europe. There is no doubt that species of HYPODERMA 

 occur there also. 



FAM. XXXIII. DEXIDAE. 



Charact. Bristle of the antennae hairy or pectinated. Thorax short. 

 First posterior cell of the wing slightly opened, sometimes closed. 

 Tegulae large. Legs long. 



The family Dexidse agrees with the Tachinidse, Sarcophagidse, 

 Muscidse, and Anthomyidse, in having the tegulse larger than any 

 of the following families of the Brachycera. These five families 

 have been therefore united under the name of Muscariae calyptratse, 

 and contrasted with the following, called Muscariae acalyptratse. 

 There is no possibility, it seems, to discover any other constant 

 character ; that which appears the most serviceable was pointed 

 out to me by Mr. Haliday; it is the transverse suture of the 

 thorax being usually of the same depth on its whole extent in 

 the Muscarise calyptratse, whereas in the Muscariae acalyptratse it 

 is generally distinct at each side and imperceptible on the middle 

 of the thorax. But as some families among the so-called Musca- 

 rise acalyptratse have the tegulse so well developed as to resemble 

 those of many Anthomyidse, a high importance cannot be attached 

 to that subdivision. Should it be maintained, the Oestridse ought 

 to be placed among the Muscarise calyptratse. 



The four families : Dexidse, Tachinidse, Sarcophagidse, and Mus- 

 cidse, agree in the first posterior cell being very much narrowed or 

 closed at the end, and differ in this from the family Anthomyidse. 

 The former have, for this reason, been comprised under the 

 common name of Creophilse, in opposition to the latter, which 

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