452 Mr. G. Meade- Waldo on 



Ducke (Zeitsclir. wiss. Ins. Biol. i. p. 175, 1905) treats of 

 the nocturnal habits of M. idaJia. Tlie same author, who 

 examined the types of Brazilian bees described by Smith 

 (Deut. ent. Zeit. p. .^63, 1910), leaves only R. idalia in the 

 genus, relegating M. hituherculata, wliich was selected by 

 Cockerell as the type (Proc. Phil. Acad. p. 374, 1900), to 

 Hulictus. Of the species described as Megalopta by Smith 

 at later dates only M. purpuraia {1819} can remain in the 

 genus, and its inclusion is open to question ; the remaining 

 species work out mainly as proposed by Ducke (/. c), e. g^ 

 M. nigrofemorata and M. ianthina go into Halictus sens, lat., 

 while M. ijilosa and M. cxiprifrons belong to the cacosoma 

 group of species in that genus. 31. ornata, a brilliant 

 metallic-green insect, has nothing whatever to do with the 

 genu?=, and probably needs a new one. M. vivax has quite 

 rightly been placed as a variety of Augochlora atropos^ 

 Smith, though I do not agree with Ducke in synonymizing 

 Augochlora with Halictus. 



Key to the Species. 

 22- 



1. (2) Black species, non-metallic. Length 



13 mm cherazon, Vach. (1904). 



2. (1) Testaceous species, head and thorax 



with some metallic iridescence. 



3. (4) Cheeks armed with a conspicuous 



tubercle ; clvpeus much broader 



than long. Length 15 mm genalis, sp. n» 



4. (3) Cheeks unarmed. 



6. (8) Enclosed area well developed ; hind 

 spur with six well-developed spines. 



6. (7) Joint 3 of antennae longer than 4, as 



long as 5. Length 17 mm fornix, Vach. (1904). 



7. (6) Joint 3 of autenntB short, not longer 



than 4. Length 14 mm sodalis, Vach. (1904). 



8. (5) Enclosed area very narrow, hardly 



more than linear ; hind spur with 

 four spines. 



9. (10) Postscutellum almost as long as 



scutellum, clypeus only sparsely 



punctured cJiaperi, Yach. (1904). 



10, (9) Postscutellum only half as long as scu- 

 tellum, clypeus coarsely punctured . idalia, Smith (1853). 



M. cuprea, Friese (1911), is possibly a variet}"^ of M. idalia. 



66. 



1. (4) Blaclr species. 



2. (3) Thorax and abdomen with faint 



coppery and purple iridescence. [= virgili, Fr. (1l,911). 

 : Length 14 mm piirpu rata, Umith {1879) 



