Megalopta Smith, 1853

ENGEL, MICHAEL S., 2000, Classification Of The Bee Tribe Augochlorini (Hymenoptera: Halictidae), Bulletin of the American Museum of Natural History 2000 (250), pp. 1-89 : 40-41

Genus Megalopta Smith

DIAGNOSIS: This is a large genus of nocturnal bees exhibiting the typical characters of large ocelli and pale integumental pigmentation. Megalopta is related to the genus Xenochlora , but this group has normal-sized ocelli, lacks the densely packed, single series of distal hamuli, and has stiff, black setae on the hindlegs. Among the other nocturnal genera, Megaloptidia and Megommation , Megalopta lacks the strongly narrowed and elongate prementum and the pointed galeal apex. The pectinate inner metatibial spur and densely packed hamuli can also separate Megalopta from other nocturnal augochlorines.

DESCRIPTION: Female. Labral distal process broadly triangular; keel expanded basally; basal elevation bilobed; teeth absent. Prementum not greatly elongate. Galeal apex rounded; galeal comb absent; galeal base extending to base of stipes. Hypostomal ridge carinate to weakly lamellate; anterior angle rounded. Malar space less than basal mandibular width. Epistomal sulcus acute, gently projecting into clypeus. Ocelli greatly enlarged; ocellar furrow present. Vertex expanded behind ocelli. Preoccipital ridge rounded. Pronotal lateral angle not produced; dorsal ridge rounded; lateral ridge carinate. Mesoscutal anterior border rounded; mesoscutal lip rounded. Tegula oval. Anterior basitarsal brush present. Inner hind tibial spur pectinate. Apex of marginal cell truncate. Distal hamuli closely and evenly spaced. Basal area of propodeum smooth or striate, strongly declivitous; propodeal pit narrow. Male. Mandible simple. Labrum with distal process; basal area not notched. Antennae extending back to scutellum, metanotum, or propodeal triangle; F2 much longer than F1. Inner hind tibial spur serrate. Apical margin of S4 emarginate medially, with lateral notches, setal patches bordering emargination. Apical margin of S5 emarginate, medial surface with tubercle fitting into emargination of S4. Apical margin of S6 emarginate. Apical margin of S7 with median process bilobed. Apical margin of S8 unmodified; spiculum narrow. Proctiger with anal filaments. Gonobasal bridge narrow; dorsal lobes weak. Parapenial lobe present; basal process of gonostylus absent. Ventral surface of penis valve with prong.

Subgenus Megalopta Smith s.s. Figures 6 , 11 , 16 , 19 , 36 , 59 , 66 , 70 , 73

Megalopta Smith, 1853: 83 . Type species: Megalopta idalia Smith, 1853 [= Halictus amoenus Spinola, 1853 ], designation of I.C.Z.N. (1966), petition by Michener and Moure (1964). Designation of Megalopta bituberculata Smith, 1853 , as the type species by Cockerell (1900) and Meade-Waldo (1916) is invalid.

Megaloptera Ashmead, 1899: 92 . Lapsus calami.

Megalopta (Megaloptella) Schrottky, 1906: 312 . Type species: Halictus ochrias Vachal, 1904 , monobasic and original designation.

Tmetocoelia Moure, 1943a: 481 . Type species: Megalopta sulciventris Friese, 1926 , original designation.

DIAGNOSIS: The nominate subgenus differs from the cleptoparasitic species of Noctoraptor by the presence of scopal hairs, a basitibial plate, and the normally developed mandibles. The apical margin of the male clypeus is white and F2 is about as long as F 3 in Megalopta s.s., while the clypeus is black and F2 is much shorter than F 3 in Noctoraptor .

DESCRIPTION: As for the genus with the following additions: Female. Mandible multidentate, with supplementary teeth. Scopa present. Basitibial plate bordered posteriorly, margin obsolete anteriorly. Male. Apical margin of clypeus white. Scape anteriorly white; F2 approximately equal in length to F3. Metasoma oval to elongate. Apical margin of S5 narrowly emarginate.

REVISIONS: Friese (1926) revised the species of Megalopta , although he included species of Megaloptidia and Megommation . There has been no modern treatment of the genus. Moure and Hurd (1987) listed 28 species, although their Megalopta ianthina and M. nigrofemorata are species of Xenochlora and were transferred to that genus by Engel et al. (1997). Megalopta intermedia , listed by Sakagami (1979) is a nomen nudum (see append. 1).

BIOLOGY: Species of Megalopta are nocturnal. Individuals can be readily captured at lights just after dusk until just before dawn (personal obs.). Brief accounts of the nesting biology of two Megalopta species have been given by Sakagami (1964) and Janzen (1968), while accounts of their seasonal abundance and nocturnal activity are given by Wolda and Roubik (1986) and Roulston (1997) respectively. Immatures for two Panamanian species are currently being studied (Engel and Wcislo, in prep.), as are finer details of the nesting and social biology of these species (W. T. Wcislo, personal commun.).

DISTRIBUTION: Megalopta s.s. ranges from southern Brazil to Mexico.

Figures

Figs. 1–6. Heads of Augochlorini, frontal aspect. 1. Thectochlora alaris (Vachal), female. 2. Rhinocorynura briseis (Smith), female. 3. Megommation (Cleptommation) minutum (Friese), female. 4 Chlerogella sp., female. 5. M. (Megaloptina) ogilviei (Cockerell), female. 6. Megalopta (Megalopta genalis Meade-Waldo, male.

Figs. 7–12. Head modifications of female Augochlorini. 7. Temnosoma metallicum Smith, dorsal aspect. 8. T. metallicum, profile. 9. T. metallicum, vertex. 10. Pseudaugochlora graminea (Fabricius), vertex. 11. Megalopta (Megalopta) genalis Meade-Waldo, vertex. 12. Clypeal apex of Megommation (Megaloptina) ogilviei (Cockerell).

Figs. 13–16. Female mouthparts. 13. Labiomaxillary complex and hypostomal fossa of Megommation (Megaloptina) ogilviei (Cockerell), ventral aspect. 14. Labiomaxillary complex and hypostomal fossa of Corynura (Corynura) chilensis (Spinola), ventral aspect. 15. Clypeus and mandibles of M (Cleptommation) minutum (Friese). 16. Mandible of Megalopta (Megalopta) genalis Meade-Waldo.

Figs. 17–20. Labra of female Augochlorini. 17. Augochlora (Augochlora) pura (Say). 18. Rhinocorynura briseis (Smith). 19. Megalopta (Megalopta) genalis Meade-Waldo. 20. Temnosoma metallicum Smith.

Figs. 34–37. Characteristics of female Augochlorini. 34. Tegula of Augochloropsis (Paraugochloropsis) sumptuosa (Smith), depicting notch on inner posterior margin. 35. Tegula of Rhinocorynura briseis (Smith). 36. Distal hamuli of hind wing of Megalopta (Megalopta) genalis Meade-Waldo. 37. Distal hamuli of Chlerogella sp.

Figs. 56–59. Metasomal modifications of female Augochlorini. 56. Metasoma of Temnosoma metallicum Smith, dorsal aspect. 57. Metasoma of T. metallicum, profile. 58. S1 of Augochlora (Augochlora) pura (Say), median apical ridge. 59. Apex of T5 of Megalopta (Megalopta) genalis Meade- Waldo, medioapical cleft of pseudopygidial area.

Figs. 64–67. Metasomal modifications of male Augochlorini. 64. Relatively unmodified sterna (S5– S6) of Neocorynura papallactensis Engel. 65. S3–S6 of Pseudaugochlora graminea (Fabricius). 66. S3– S6 of Megalopta (Megalopta) genalis Meade-Waldo. 67. T7 of Temnosoma metallicum Smith.

Figs. 68–71. Hidden and fused male sterna S7–S8; spicula are on the left margin and apical processes are shown on the right. 68. Augochloropsis (Paraugochloropsis) sumptuosa (Smith). 69. Temnosoma metallicum Smith. 70. Megalopta (Megalopta) genalis Meade-Waldo. 71. Pseudaugochlora graminea (Fabricius).

Figs. 72–77. Male genitalic structures. 72. Genital capsule of Thectochlora alaris (Vachal), ventral aspect. 73. Genital capsule of Megalopta (Megalopta) genalis Meade-Waldo, ventral aspect. 74. Genital capsule of Rhinocorynura briseis (Smith), ventral aspect. 75. Gonocoxite-gonostylus junction in R. briseis depicting basal gonostylar process on ventral surface, process with strong setae at apex. 76. Penis valve of Temnosoma metallicum Smith, profile, with large dorsal processes. 77. Basal gonostylar process of Corynura (Callistochlora) prothysteres (Vachal) lacking setae, partially hidden by setose ventral