PSYCHE 



VOL. XXVI JUNE. 1919 No. 3 



A PROPOSED NOMENCLATURE FOR THE PARTS OF 

 THE POSTERIOR RESPIRATORY APPARATUS OF 

 DIPTEROUS LARV.E AND A MICRO-PROTRACTOR 

 USEFUL IN THEIR DESCRIPTION.^ 



By C. L. Metcalf 



It has been pretty generally recognized that the most serviceable 

 diagnostic character for the specific determination of Dipterous 

 larvae of certain families is the posterior respiratory apparatus, 

 which varies endlessly in the different genera and species, but ap- 

 pears to be very constant wnthin the species. So superior are the 

 characteristics drawn from this part of the larva, that I regard most 

 descriptions which omit consideration of them as practically worth- 

 less. For in most cases the general features of shape, color, etc., 

 may be found to apply almost equally well to other species. The 

 most available, absolutely diagnostic characters are to be found on 

 the posterior stigmata. 



This apparatus consists, in many species, of three pairs of spir- 

 acles, generally more or less elongate or linear, and a fourth pair of 

 circular structures (usually present) referred to in literature as 

 "buttons" or "circular plates."- This respiratory organ varies in 

 the different families, genera and species in height; in width; in 

 extent of elevation above the surface of the segment which bears 

 it; in the ornamentation of the interspiracular spaces (vide infra); 

 in length and width of the slit-like spiracles, which may be straight, 

 curved, sinuate or denticulate, and variously arranged with respect 

 to the median line and to each other; in the presence or absence of 

 the circular plate, its position and diameter; and in many other 

 ways. 



1 Contributions from the Entomological Laboratory of the Bussey Institution, Harvard 

 University, No. 160. 



2 In those rarer cases (as e. g., (Estris oris) where the three pairs of spiracles appear to be 

 wanting, only a part of the following characteiistics will be found to be applicable. 



