DIPTERA FROM NEPAL 121 



2. Sex-combs are present but the hooked scaly bristles absent (ananassae and 

 melanogaster subgroups, obscura group). Stage 3. Sex-combs are better developed, 

 inducing homeotic expression of the hooked scaly bristles (suzukii and takahashii 

 subgroups, D. (T.) gracilis). Stage 4. Sex-combs are further well developed, the 

 hooked scaly bristles being compensatorily weakened in expression (ficusphila 

 subgroup). Stage 5. Further compensation is pronounced, resulting in disappear- 

 ance or non-development of the hooked scaly bristles (montium and nipponica 

 subgroups). 



Fig. 328 



Compensation 

 HSB 



Stage 



anan suzu f - mont 

 Mam ^meU taka ™PP , T ^ m 



Obsc MelaT 



Fig. 328. Homeotic and compensatory relationships between the hooked scaly bristles 

 (HSB) of male mid leg and the sex-combs (SC) of male fore leg. Mela., melanogaster 

 group ; Obsc, obscura group ; Momm., mommai group ; Will., willistoni group ; 

 anan., ananassae subgroup ; ficus., ficusphila subgroup ; mela., melanogaster subgroup ; 

 mont., montium subgroup ; nipp., nipponica subgroup ; suzu., suzukii subgroup ; 

 taka., takahashii subgroup. For further explanations see text. 



C. Homology in the components of phallic organs and the systematic 



ANALYSIS OF PHALLIC FORMULAE 



As is frequently stressed, the phallic organs of insects are systematically and 

 diagnostically essential key characters. Their extensive diversification, however, 

 makes it often difficult to establish homology of their components even between 

 closely related taxa. Those of Drosophilidae are not exceptional, e.g., the present 

 author (1956) considered the ventral recurved process of aedeagus (u) of the genus 



