Introduction

Members of the genus Megachile are among the best known bees (O’Toole & Raw 1991). Here I have followed Michener et al (1994, 2000) and treated the group as a single genus combining Megachile with Chalicodoma. Most are called "leaf-cutter bees" because the females cut leaves and petals to line their nests. Others are the "mason bees" because they construct their nests with resin, mud or leaves chewed into pulp. The neotropical species are from half to three times the length of a honeybee.

The aim of this inventory is to disentangle some of the great confusion that exists over the identification of the species of Megachile of the Neotropics. Identification to subgenus and knowledge of the geographical distributions of the members of the subgenus substantially reduces the number of options and assists identification to species or species group. I hope easier identification will stimulate studies on the bees’ biology and enable researchers to better assess their roles as pollinators.

For each species the subgenus is indicated, the valid name and changes of names are listed and information on the bee’s biology and its geographical distribution are given. The subgenera are indicated to which 395 neotropical species belong, including 9 Old World species introduced to the region during historical times. Dalla Torre (1896) listed 92 neotropical species now included in the genus Megachile. Three neotropical species were erroneously placed at some time in the genus Megachile. Their present statuses are indicated below. There are also five nomina nudae. Nomenclatural questions of subgenus or species groups and of subspecies are not discussed.

Species of Megachile can be placed with certainty in their correct subgenera only by examining the type specimens. Nonetheless, a number of authors have done so without stating the situation. In order to improve the authority of this work, to date I have examined 246 type specimens of neotropical Megachile. In all the cases where “Examined” is stated I have seen the holotype. In those cases where I have not done so, the basis of my decision is clearly stated.