Taxonomic
review
The genus Megachile was created by Latreille in 1802 and, as originally
conceived, it was equivalent to the present family Megachilidae
which comprises one of the largest groups of bees. Of the species
which Latreille included in Megachile today only the European
species, M. centuncularis and M. lagopoda remain.
Very soon, various authors began to divide up Latreille’s genus into new genera.
The first were Anthidium by Fabricius (1804), Osmia
and Stelis by Panzer (1806), Heriades by Spinola (1808)
and Latreille, himself, proposed Coelioxys in 1809. Westwood
(1840) designated the European species Apis centuncularis
Linnaeus as the type of the genus Megachile. Lepeletier
(1841) erected the genus Chalicodoma for the species whose
body shape and mandibles differed from typical Megachile,
but Mitchell (1934) returned it to the latter genus. Creightonella
was created as a subgenus of Chalicodoma by Cockerell (1908a).
Michener (1962) re-examined the groups and recognized the genus
Megachile as "leaf-cutter bees" and Chalicodoma
as "mason bees". However, on a global scale there are
many exceptions which cast doubt on the division between Megachile
and Chalicodoma. Therefore, in recent works Professor Michener
(Michener et al 1994, Michener 2000) has combined the two
taxa in a single genus and in the present work I have followed this
concept of the genus.
According to Professor Michener (2000:
67) cited 1,095 species of Megachile world-wide. I feel
he was being cautious. At the start of the present work I compiled
a list of 2,645 specific names. Professor Michener listed 366 species
from the Americas (74% of the present total).
In such a large genus, division into smaller, manageable groups is essential
in pursuing the alpha taxonomy with any confidence. Progress has
been made at this level with the erection of 53 subgenera (Michener
op. cit). To date, 73 divisions have been proposed. With nearly
30 publications between 1926 and 1980, Professor T. B. Mitchell
has made by far the greatest contribution to our knowledge of New
World Megachile. He divided the American members into subgenera
(Mitchell 1934, 1935, 1935b, 1936, 1937a, 1937b, 1937c, 1937d, 1943b,
1980) and, in so doing erected 18 of the Hemisphere’s 30 subgenera.
In his last work (Mitchell 1980) he divided the group into six genera,
however, we still know little of the higher taxonomy of the group
and these divisions are difficult to justify. All recent authors,
including Professor Mitchell, cite numerous exceptions in their
keys and Mitchell changed his opinion on the presence of some critical
characters in several subgenera (notably Leptorachis) between
1943 and 1980. Some others have published important works on the
neotropical members of the genus. The more notable are Schrottky
(1913a), Friese (1911) and Hurd (1979). However, the neotropical
species still present many taxonomic questions.
The known distributions of several species are questionable. Examples are
Megachile (Austromegachile) antiqua , M. (Austromegachile)
exaltata , M. (Austromegachile) montezuma , M.
(Chrysosarus) vestis , M. (Neochelynia) aegra
, M. (Neochelynia) chichimeca, M.
(Pseudocentron) prietana and M. (Sayapis)
zaptlana. Even in Brazil there are some surprising distributions.
M. (Acentron) eburneipes is recorded from southern states
north to Mato Grosso and Minas Gerais and from Rio Grande do Norte.
The data on these species suggest there has been inadequate collecting
or patchy geographical distributions or misidentifications.
To date, 515 species of the Americas have been allocated to 30 subgenera (Table
1). The neotropical species of Megachile comprise 395 species
in 26 subgenera (Table 1). Hurd (1979) catalogued 133 members of
the genus which occur in Canada and U.S.A. (as Megachile and
Chalicodoma). Michener (2000) recognised 13 subgenera from
North America of which 4 do not reach the Neotropics. Three are
confined to the nearctic (Grosapis Mitchell, Megachiloides
Mitchell and Xanthosarus Robertson), while the subgenus
Megachile is holarctic. The monotypic subgenus Grosapis
is nearctic, confined to the north of Mexico (Cockerell 1934: 3;
Mitchell 1930: 292) and was not included in Dr. Hurd’s inventory.
The number of nearctic species now stands at 130 of which 11 also
occur in the Neotropics. An additional 90 names in Megachile
have been recorded from the Americas, but the whereabouts of the
types are not known.
Subgenus |
Restricted to neotropics |
Both realms |
Restricted to nearctic |
Total Americas |
Total neotropical |
Acentron |
21 |
1 |
|
22 |
22 |
Argyropile |
|
2 |
6 |
8 |
2 |
Austromegachile |
37 |
|
|
37 |
37 |
Callomegachile |
4 |
|
|
4 |
4 |
Chelostomoides |
16 |
1 |
17 |
34 |
17 |
Chrysosarus |
51 |
|
|
51 |
51 |
Cressoniella |
19 |
1 |
|
20 |
20 |
Dasymegachile |
13 |
|
|
13 |
13 |
Eutricharaea |
2 |
1 |
2 |
5 |
3 |
Gronoceras |
1 |
|
|
1 |
1 |
Grosapis |
|
|
1 |
1 |
0 |
Leptorachis |
38 |
|
|
38 |
38 |
Litomegachile |
1 |
|
5 |
6 |
1 |
Megachile |
|
|
5 |
5 |
0 |
Megachiloides |
|
|
59 |
59 |
0 |
Melanosarus |
10 |
|
1 |
11 |
10 |
Moureapis |
30 |
|
|
30 |
30 |
Neochelynia |
17 |
|
|
17 |
17 |
Pseudocentron |
68 |
2 |
3 |
73 |
70 |
Pseudomegachile |
1 |
|
|
1 |
1 |
Ptilosaroides |
2 |
|
|
2 |
2 |
Ptilosarus |
15 |
|
|
15 |
15 |
Rhyssomegachile |
3 |
|
|
3 |
3 |
Sayapis |
21 |
3 |
6 |
30 |
24 |
Schrottkyapis |
1 |
|
|
1 |
1 |
Stelodides |
1 |
|
|
1 |
1 |
Trichurochile |
3 |
|
|
3 |
3 |
Tylomegachile |
6 |
|
|
6 |
6 |
Xanthosarus |
|
|
15 |
15 |
0 |
Zonomegachile |
3 |
|
|
3 |
3 |
Total |
384 |
11 |
120 |
515 |
395 |
Percentage |
74,6 |
2,1 |
23,3 |
|
|
Table 1. The extant species of Megachile of the Americas
arranged by subgenus
|