1.The following new species of Asca were described and figured: A. garmani (North America, West ludies, Hawaii); A. brachychaeta (USA.); A . citri (Florida); A. incisa (Florida); A. muma (l (Florida, Cuba); A . neopallida (USA.); A . piloja (Maryland); A. pini (Mexico); A. spicata (Hawaii). The type specimens of A. duosetosa Fox (Puerto Rico, Florida), A. elongata (Berlese) (Florida), and A. quinquesetosa Wharton (Hawaii, Clipperton Island) were redescribed. North American specimens of the following species formerly known from Europe were described: A. aphidioides (L.), A. nova Willmann and A. nesoica Athias-Henriot. The identity of A. bicornis (Can. and Fanz.) is uncertain. 2. Seasonal and geographic variation were noted for sorne species. Females of A . aphidioides from Maryland collected in May and June were larger and had longer setae than females collected at other times of the year. Individuals of A. garmani and A. brachychaeta from Connecticut and Maryland were larger than those from Florida. A . garmani from Quebec were smaller than those from northern Connecticut, however. 3. Reasons for considering Asca to be more closely related to Leioseius and Gamasellodes than to Digamasellus were discussed.