44 Acarology 



A key to the groups of the Mesostigmata modified from Tragardh 

 1946 follows: 



Key to the Mesostigmata 



1. Well-developed epigynial plate present in females, or if reduced 



or lacking its function taken over by median plate or lateral plates 2 



Epigynial plate primitively absent in females; median and lateral 

 plates not closing genital opening 8 



2. Lateral plates present 3 

 Lateral plates absent 4 



3. Discrete metasternal plates present Celaenopsina 

 Metasternal plates combined in sternal plate Fedrizziina 



4. Epigynial plate hinged or fused to ventral plate along transverse 

 suture, or peritreme ventral, or both 5 



Epigynial plate not articulated at base, peritreme dorsal 



Thinozerconina 



5. Epigynial plate with one pair of genital setae 6 

 Epigynial plate without setae 7 



6. Male genital aperture surrounded by sternal plate; metasternal 

 plates reduced so that only metasternal setae apparent; chelicerae 



of males not modified for copulation Zerconina 



Male genital aperture in front of sternal plate; metasternal plates 

 varied; chelicerae of males more or less modified to transfer 

 spermatophores during copulation Gamasides 



7. Metasternal plates distinct Trachytina 

 Metasternal plates greatly reduced or lacking 10 



8. Presternal setae not present; female genital opening transverse slit 9 



Presternal setae flanking tritosternum; female genital opening 

 crescentic fissure between sternal and ventral plates Megisthanina 



9. Female genital opening large, between sternal and ventral plates 



Liroaspina 



Female genital opening small, with no connection with either 

 sternal or ventral plates Microgyniina 



10. Presternal setae flanking tritosternum Diarthrophallina 



Presternal setae not present Uropodina 



