THE FLIES THAT CAUSE MYIASIS IN MAX 



143 



Figure 84. — A, Psychoda altemata, denuded wing, to show venation; B, P. 

 alternate terminal antennal segments; C, P. alMpennis, terminal antennal 

 segments. (After Tonnoir [150).) 



Figuee 85. — Psychoda alt e mat a, larva. (After Johannsen (61, pi. 12, no. 99).) 



be studied from specimens mounted in the ordinary way ; for positive 

 identifications cleared specimens mounted on microscope slides may 

 be necessary. 



Johannsen (61. p. 23) gives a key to larvae. For adults see Del 

 Rosario (125) for the American species and Tonnoir (1-50, 151) 

 for the European species. 



PSYCHODA ALBIPENMS Zetterstedt 



Recognition Characters. — Adult : This is a medium-sized species, about 1.25 

 mm. in length. The antenna (fig 84. C) is 15-segmented ; the thirteenth seg- 

 ment is subglobular ; the last two are rather closely conjoined, net globular, and 

 very small, their combined length being less than that of the thirteenth ; the 

 fourteenth segment lacks pubescence. The wings are unmarked : the two main 

 forks are complete at the base. 



Geographical Distribution. — Palaearctic Region : Scotland. England, France, 

 Netherlands, Belgium, Norway. Sweden. Austria. Ethiopian Region : Seychelles. 



Biology and Pathogenesis. — The larvae are found in moist places, 

 such as ditches, decaying moist vegetable matter, decaying fruit, the 

 sides of drains, and in filter beds of sewage-disposal plants, where they 

 may occur very abundantly on the bacterial film. 



Patton and Evans (111. p. Jf.87) have reported a case of urinary 

 myiasis in a boy in Scotland. Larvae were passed with the urine and 

 others were extracted from the bladder with a cystoscope: the bladder 

 appeared inflamed. As the boy admitted having eaten moist earth, 

 the authors concluded that the larvae were ingested in this way and 

 had burrowed from the rectum into the bladder : it is more probable, 

 however, that infestation occurred directly through the urinary 

 passages. 



PSYCHODA ALTERNATA Say 



Synonym. — Psiichoda sexpunctntn Curtis. 



Recognition Characters. — Adult : Tins is a moderately large species, about 1.5 

 mm. in length; the wing (fig. S4. A) has a mottled appearance, with black spots 

 formed of tufts of black hairs at the apices of certain wing veins ; three or four 



