68 AMERICAN DIPTERA. 



The costal spines in Heteromyza are said to be very small, but 

 there seems to be no good reason for regarding this as a North 

 American genus, and we have not taken it into account. 



The larval habits are known in only a few cases in our fauna. 

 Some of the species are found in caverns, where the larvse are said 

 to breed in the excrement of bats. The adults of others are found 

 about the mouths of holes occupied by rodents ; other species are 

 adapted to life on sand dunes. The known habits are mentioned 

 under the separate species. 



The classic paper on the family is Loew's " Ueber die europiiis- 

 chen Helomyzidse und die in Schlesien vorkommenden Arten der- 

 selben," published in the Zeitschrift fiir Eutomologie, xiii, 1-80. 

 The work bears the date 1859, but as determined by Osten Sacken 

 and Czerny it must have been published in 1862 or early in 1863. 

 There appear to be no names of about that period conflicting with 

 Loew's, hence the exact date is not of great importance. Schiner's 

 treatment of the family in Fauna Austriaca, Diptera, ii, 20-35, 

 1864, really antedates in its preparation the paper by Loew ; hence 

 it is practically superseded by the latter, especially in the matter of 

 genera. The only other general work on the family is a recent one 

 by Czerny, " Revision der Helomyziden," in Wiener Entomologische 

 Zeitung, xxiii, 199-244 and 263-286, published in 1904. This 

 includes the Helomyzinse (only the genera Helomijza and Allo- 

 phyla), being Part I of a work as yet unfinished. The descriptions 

 of the American species are quoted ; one useful feature of the work 

 is a set of notes on Walker's types of Helomyzidse, showing that 

 none of the species belong to the family at all, unless it may be 

 among the small number of which the types are now missing. 

 Nearly all are Sapromyzas. 



Loew based his classification mainly on characters derived from 

 the bristles ; hence this was the first family in which chsetotaxy was 

 used, and that long before the introduction of the term. 



The bristles which by their variability afford generic characters 

 are first of all the dorso- centrals, which occur in all the numbers 

 from one to five ; the humeral and propleural (either one each or 

 absent) are also useful. The figure on Plate III shows the position 

 of the various parts and bristles of the thorax. 



Important specific characters are found in the number of sterno- 

 pleural bristles, the presence or absence of hair or bristles on the 



