ANATOMY. 19 



eggs that I have seen, with the possible exception of those of Leuco- 

 phenga varia. These structures are, however, different in number and 

 shape in the different species, and afford excellent specific characters. 

 They lie spread over the surface of the food when the egg is laid 

 normally, and apparently keep the anterior end of the egg from sinking 

 below the surface. 



The micropyle is situated in the small papilla that can be seen at 

 the anterior tip of the egg. The sperm probably enters here. 



The larva emerges from the anterior end of the egg, squeezing 

 through an irregular opening formed by a split in the chitinous shell 

 of the egg. 



The eggs known to me may be classified as follows : 



1. Eight or more filaments Chymomyza 3 



Two, three, or four filaments 2 



2. With a ridge above; filaments short Scaptomyza 4 



No ridge on upper side Drosophila 5 



3. Usually eight filaments C. procnemis 



Ten filaments C. amoena 



4. Two filaments ."> . graminum 



Four filaments S. adusta 



5. Three filaments 6 



Two filaments 7 



Four filaments 8 



6. Median filament sUghtly thicker than either of the two lateral ones D. quinaria 



Median filament more than twice as thick as either of the two lateral ones . . D. transversa 



7. D. affinis, D. caribbea, D. earlei* D. melanica, D. melanogasier, D. nebulosa, D. 



obscura, D. simulans. 



8. D. busckii, D. cardini, D. funebris, D. hydei, D. immigrans, D. putrida, D. repleta, 



D. robusta, D. similis* D. torrei, D. tripunclata* D. virilis. 



Anterior filaments are described for the eggs of the genus Scatophaga 

 (Cordylurinse), but are absent in the described Calypterse, Trypetinse, 

 and Agromyzinse. 



LARV^. 



Various drosophiline larvae have been more or less thoroughly de- 

 scribed by Heeger (1851), Comstock (1893), Howard (1900), Unwin 

 (1907), Martelli (1910), Johannsen (1910), Banks (1912), Keilin (1915), 

 and de Meijere (1916). 



According to Keilin, the larvae of D. melanogaster pass through 

 three stages, separated by two larval molts. As in most other cyclo- 

 rhaphous Diptera, the anterior spiracles do not appear until after the 

 first molt, and the cephalopharyngeal skeleton becomes larger and 

 stouter at each molt. The first-stage larvae have a chitinized median 

 plate, dorsal to the pharynx and just behind the mouth-hooks, which 

 is not present in the second or third stage larvae. Keilin has seen this 

 plate also in first-stage larvae of Borborinae and Sepsinae. 



* The eggs of these species I have not seen. The number of filaments is given on the authority 

 of Dr. C. W. Metz. 



