The species _ater_ and _pretiosus_ differ mainly in size (Table 4), some measurements clearly separating the two when sexual dimorphism is considered. Also, the average weights of 18 nonpregnant females and four males of _pretiosus_ (all adults) collected on 20 February 1968 at Los Cocos, were 20.9 (14.6-23.8) and 27.0 (24.6-31.7) gms, respectively, significantly smaller than corresponding figures for 11 nonpregnant females and nine males of _M. a. nigricans_ taken two weeks later on the Cosigüina Peninsula--29.1 (26.1-33.0) and 32.9 (29.3-35.1) gms. It is of note that we have not collected these two large species at the same localities in Nicaragua, and it is possible that one competitively excludes the other in local situations. TABLE 4.--Selected measurements of adults of three species of _Molossus_ from Nicaragua. Table Legend: Col. A: Number of specimens averaged or catalogue number, and sex Col. B: Length of forearm Col. C: Greatest length of skull Col. D: Condylobasal length Col. E: Zygomatic breadth Col. F: Breadth of braincase Col. G: Length of maxillary toothrow Col. H: Breadth across upper canines ==================================================================== A B C D E F G H -------------------------------------------------------------------- _Molossus ater nigricans_, Departamento de Chinandega, Nicaragua Average 10 ([Male]) 49.5 23.2 20.2 14.3 11.0 8.2 6.1 Minimum 48.2 22.8 19.9 14.1 10.5 8.0 6.0 Maximum 50.7 23.5 20.5 14.9 11.2 8.3 6.3 Average 10 ([Female]) 49.0 22.0 19.2 13.6 10.7 7.8 5.8 Minimum 47.1 21.5 18.8 13.3 10.5 7.6 5.6 Maximum 51.2 22.5 20.0 14.1 11.0 8.2 6.1 _Molossus pretiosus pretiosus_, Departamento de Boaco, Nicaragua Average 8 ([Male]) 45.1 21.7 18.8 13.4 10.6 7.6 5.9 Minimum 44.1 21.0 18.3 13.1 10.2 7.4 5.6 Maximum 46.1 22.2 19.1 13.7 10.9 7.9 6.1 Average 23 ([Female]) 43.6 20.2 17.7 12.5 10.1 7.3 5.2 Minimum 41.0 19.5 17.2 12.2 9.5 7.1 5.0 Maximum 44.8 20.7 18.2 13.1 10.4 7.6 5.6 6 mi SW Managua, Nicaragua KU 70135, [Male] 44.8 21.7 18.6 13.0 10.2 7.7 5.8 KU 70137, [Male] 45.1 21.6 19.0 13.2 10.7 7.7 5.8 KU 70136, [Female] 43.5 19.9 17.8 12.7 10.3 7.5 5.5 3 km N, 4 km W Diriamba, Nicaragua Average 7 ([Male]) 44.8 21.2 18.5 13.0 10.5 7.4 5.5 Minimum 43.8 20.7 18.3 12.7 10.2 7.2 5.4 Maximum 45.7 21.3 18.8 13.3 10.9 7.6 5.5 Average 9 ([Female]) 44.0 20.7 18.0 12.6 10.2 7.3 5.3 Minimum 42.0 20.0 17.4 12.0 10.0 7.0 5.0 Maximum 45.5 21.2 18.6 13.0 10.6 7.5 5.5