122 T. OKADA 



Leucophenga (p. 17) to be the main part of the aedeagus. The present research 

 revealed the real homology in the components of aedeagus between the genera 

 Leucophenga and Microdrosophila. Microdrosophila nigrohalterata (p. 41) and 

 M. marginata (p. 42) have the ventral recurved process well developed as in Leuco- 

 phenga, and the former species shows the posterior parameres contiguous to the 

 subapical part of aedeagus (Text-fig. 117) as in Leucophenga. The facts indicate 

 that these two genera are closely related, and this is confirmed by the analysis of 

 phallic formulae. 



As a means to analyse phallic formulae the ideas of " divergency index " (d.i.) and 

 " difference value " (d.v.) (Okada, 1954, 1956) have been taken into consideration. 

 The d.i. is a sum of values o, -5, 1 -o, and 2 -o afforded to a large letter, small letter 

 with dash, small letter, and small letter with attached respectively, in the phallic 

 formula. The phallic formula of a higher taxon is obtained by calculating mean value 

 for each letter of the member species. The d.v. means a sum of differences in value 

 for each of corresponding letters between two taxa. 



The phallic formula and d.i. thus determined for each genus or subgenus are as listed 

 below. The d.v. between every two genera or subgenera is shown in Tables 3 and 4. 



Genus or 

 Subgenus 



Number oJ 



species 

 examined 







phallic formula 





d 



1. 



Cryptochaetum 



1 



a' 



BCd, 



E 



fo 



goH 



I k 



L 



m n 



95 



Diastata 



1 



a 



BCD 



E 



f 



g H 



i k 



L 



m N 



6 







Campichoeta 



1 



A 



BCD 



E 



F 



g H 



i k 



L 



M N 



3 







Apsinota 



1 



a 



BCd 



e 



f 



goH 



i k 



1 



M N 



9 







Leucophenga 



10 



A 



BCD 



e 



F 



g H 



i k 



L 



m N 



5 







Microdrosophila 



2 



a 



b'Cd 



e 



F 



g H 



i k' 



1' 



m n 



8 



5 



Liodrosophila 



4 



a 



BCd 



E 



f 



goH 



I k 



1 



m N 



8 







Paramycodrosophila 



1 



a 



b C d 



E 



f 



g H 



I k 



1 



m'N 



7 



5 



Chaetodrosophilella 



1 



a 



BCd 



E 



f 



g H 



I K 



1 



M N 



5 







Scaptomyza 



3 



a 



b'Cd 



E 



f 



goH 



i k 



L 



m n 



9 



5 



Diathoneura 



1 



a 



BCd 



E 



*o 



g H 



i K 



L 



m N 



7 







Drosophila 



21 



a' 



B c' d' 



e' 



f 



g H 



i' k' 



1' 



m N 



6 



5 



Scaptodrosophila 



3 



A 



BCd' 



e 



f 



g H 



I k' 



L 



M N 



3 



5 



Dichaetophora 



2 



a 



BCd' 



e' 



f 



goH 



I k 



1' 



m' n' 



7 







Hirtodrosophila 



1 



a 



B c D 



E 



fo 



gH 



i K 



1 



M N 



7 







Sophophora 



7 



A 



B c' D 



E 



f 



g H 



i' K 



L 



M N 



3 







Drosophila s. str. 



8 



a 



BCd 



e' 



f 



g„H 



I k 



1 



m'n' 



8 



5 



The genus Leucophenga shows d.v. with Microdrosophila 4-5, which is the lowest 

 among the values shown between Leucophenga and any genus of Drosophilinae 

 (Table 3). Although the d.v. between Leucophenga and Drosophila is also 4-5, this 

 low value is due to high diversification of the phallic organs among the species of 

 Drosophila. Indeed, except with the subgenus Scaptodrosophila, Leucophenga shows 

 d.v. higher than 4 -5 with each subgenus of Drosophila. 



The analysis of phallic formulae also indicates that among the genera of Diasta- 

 tidae, Diastata is nearer to Campichoeta than to Apsinota, the d.v. between Diastata 

 and Campichoeta (3 -o) being smaller than that between Campichoeta and Apsinota 



