228 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



one, and it is not improbable that my specimens from the Chaco and 

 from northern Paraguay are in the same category. 



The present species seemed to be partially migratory. In the 

 Chaco it was recorded near the Riacho Pilaga, Formosa, on August 

 13 and 14, 1920, while on the wooded hill at Kilometer 25, Puerto 

 Pinasco, I found it common on September 1. The species was found 

 only on September 15 near Kilometer 80, but was recorded again 

 on the Cerro Lorito opposite Puerto Pinasco on September 30. The 

 birds were usually found about flowers in heavy forests, though oc- 

 casionally they searched for insects over the bark of trees or came 

 to the blossoms of lapacho trees {Tecoma obtusata) that grew at the 

 border of the monte. They were nervous and excitable, and on sev- 

 eral occasions darted swiftly at my head when I was squeaking to 

 call up other birds. In feeding they worked actively at flower 

 clusters for several minutes and then rested on perches protected by 

 overhanging leaves. In flight their wings produced a loud rattle, 

 and in addition the hummers made a metallic sound, composed of a 

 series of rapid notes that were plainly vocal since the throat was in 

 movement as they were uttered. Often when the birds scolded from 

 a perch the wings were extended wide for a few seconds and then 

 drawn in again to the body. A male shot September 15 had the 

 testes enlarged about one-half. 



The bird was Imown in the Guarani tongue as mainumhii. 



CHLOROSTILBON AUREO-VENTRIS (d'Orbigny and Lafresnaye) 



Ornismya anreo-ventris cI'Orbigny and Lafresnaye, Mag. Zool., vol. 8, 1838. 

 cl. 2, p. 28. (Moxos, Cochamba, Bolivia.) 



An adult male of this hummer taken at Rio Negro, Uruguay, 

 February 14, 1921, lacks the distinct coppery reflections of the 

 undersurface found in specimens from Argentina, and is smaller so 

 that it agrees with what is currently known as egregius.^^ This 

 bird has the following measurements: Wing, 50.4; tail, 30.6; ex- 

 posed culmen, 18.8 mm. An adult male from Lazcano, Uruguay, 

 shot February 6, and an adult female taken January 26, near San 

 Vicente, Uruguay, while not wholly similar to skins from Argen- 

 tina, agree with them closely. Of a pair from the Riacho Pilaga, 

 Formosa, secured August 11 and 14, 1920, the male is smaller than 

 those from Buenos Aires, as its wing measures 51 mm. and the ex- 

 posed culmen, 17.7 mm. Three immature birds from Tapia, Tucu- 

 man (April 7, 8, and 13, 1921), have the bill distinctly duller in color 

 than adults. One male has an extensive area of the green adult 



^ ChlorostiWon cgrcgius Heine, Journ. fiir Ornitli., 18G3, p. 197. (Sao Joao deJ Rey, 

 Minas Geraes, Brazil.) Tlie type locality of this bird lias been cited as Taquara, 

 though Heine states distinctly that he described it from two skins in the Berlin Museum 

 secured by Sellow at Sao Joao del Rey. 



