FAMILY FORMICARIIDAE 189 



opening at the top. It is composed of leaves and fibers and is slung 

 below the fork of a drooping slender branch or vine." Both sexes 

 build and share the incubation, with the female on the nest through 

 the night. The two eggs in one set were dull white, spotted with 

 reddish brown with the markings heaviest on the large end. One set 

 of two measured 20.6x14.3 and 21.4x15.1 mm. Another single 

 egg was spotted only on the larger end. It measured 19.4 X 14.3 mm. 

 The young on hatching are black and bare of down. 



CERCOMACRA TYRANNINA RUFIVENTRIS (Lawrence) 



Disythamnus (sic) rufiventris Lawrence, Ann. Lye. Nat. Hist. New York, vol. 

 8, 1865, p. 131. (Line of Panama Railroad, Caribbean slope, Canal Zone, 

 Panama.) 



Characters. — Lighter colored ; adult male, paler throughout ; slate 

 color above, grayish slate color underneath ; female lighter brown 

 above, lighter rufous on under surface. 



A male taken on Cerro Galera, Canal Zone, January 8, 1961, had 

 the iris light buffy brown ; bill black ; tarsus, toes, and claws dark 

 neutral gray. Another of this sex, collected at Canita, Panama, 

 February 6, 1962, had the iris dark mouse brown; bill black; tarsus, 

 toes, and claws neutral gray. A third from the old Tacarcuna village 

 site, on the upper Rio Tacarcuna, Darien, March 7, 1964, had the iris 

 mouse brown ; base of gonys fuscous ; rest of bill black ; tarsus and 

 toes bluish neutral gray ; claws dark neutral gray. 



In a female taken with the male from Cerro Galera, Canal Zone, 

 the iris was pale brownish bufif ; maxilla fuscous, mandible dull buffy 

 white, with a narrow line of neutral gray on either side from base to 

 near tip where the two joined ; tarsus, toes, and claws dark neutral 

 gray. One taken at Canita, Panama, February 6, 1962, had the iris 

 dark brown ; maxilla, except cutting edge, fuscous-black ; cutting 

 edge and mandible brownish white ; tarsus, toes, and claws neutral 

 gray. 



Measurements. — Males (10 from Canal Zone, Panama, San Bias, 

 and Darien), wing 59.9-63.2 (61.4), tail 53.3-57.3 (55.5), culmen 

 from base 16.7-19.7 (17.9), tarsus 21.5-23.1 (22.4) mm. 



Females (10 from Canal Zone, Panama, San Bias, and Darien), 

 wing 57.0-63.0 (59.3), tail 54.0-58.6 (55.3), culmen from base 

 17.1-18.7 (17.8), tarsus 22.5-23.3 (23.0) mm. 



Resident. Common in tropical lowland forests from eastern 

 Chiriqui (San Felix), on the Pacific slope, and the Rio Indio near 

 the eastern border of western Colon, and northeastern Code on the 



