178 BULLETIN 17 9, UNITED STATES NATIONAL MUSEUM 



extremes measure 18.6 by 14.0, 18.1 by 14.7, 16.0 by 13.0, and 17.0 

 by 12.3 millimeters. 



Plumages. — Dr. Dwight (1900) says that the natal down is 

 "brownish olive-green." He says of the juvenal plumage: "Upper 

 parts, sides of head and throat, an obscure pectoral band, and lesser 

 wing coverts olive-green, tlie crown feathers centrally darker. 

 Wings and tail deep olive-brown; median and greater wing coverts 

 edged with rich buff yellow forming two distinct wing bands, sec- 

 ondaries narrowly and tertiaries broadly edged with yellowish white. 

 Below sulphur-yellow, including the orbital ring." 



C. J. Maynard (1896) says that the nestlings are "quite slaty 

 above, and much lighter below [than fall juvenals], being nearly 

 white, and the darker areas are slaty." Dickey and van Rossem 

 (1938) write: 



The postjuvenal plumage (the "first winter plumage") is, as supposed by 

 Dwight, not fully acquired until very late in the fall. A specimen taken October 

 8 is still largely in juvenal feather ventrally, while one taken November 30 

 still shows many juvenal feathers on the lower throat. This is the last part 

 of the body plumage to be replaced. The juvenal remiges and rectrices are 

 retained until April. In early April there commences a complete spring molt 

 (the "first prenuptial") which involves the entire body and the replacement 

 of the old, worn juvenal wing and tail feathers. A specimen collected April 6 

 has just commenced this molt and six others, taken between April 22 and 

 April 30, represent every stage to its completion. 



The adults vary a good deal in the time of completion of the fall 

 molt. * * * In the present adult series, two specimens taken December 

 1 and 7, respectively, have nearly finished the body molt. The wing molt is 

 extremely slow and, starting as it does about the time the last of the new 

 body plumage has been acquired, takes most of the winter and early 

 spring. * * * Thus the wing replacement fills in, roughly, the time interval 

 between the winter (postnuptial) and spring (prenuptial) molts. The com- 

 plete, spring, body molt of the adults (and juveniles) begins in late March 

 and Is finished by the end of April." 



Food. — Professor Beal (1912) examined the stomachs of 103 

 yellow-bellied flycatchers, in which the contents were practically 

 97 percent animal matter and 3 percent vegetable matter. He says 

 that "its bill of fare includes insects of a number of species which 

 are injurious to garden, orchard, or forest, as the striped squash 

 beetle, several species of weevils, tent caterpillars, and leaf rollers." 

 Beetles amount to 16.53 percent, with less than 2 percent of useful 

 species. He continues: 



Hymenoptera amount to 46.25 percent of the food and were found in 81 

 stomachs. Of these, 48 contained ants, which amounted to 13.42 per cent of 

 the whole. * * * This bird is probably the greatest eater of ants of any 

 of the fiycatchers and stands near the head in the eating of Hymenoptera 

 in general. * • * Hemiptera were found in 33 stomachs only, and amount 

 to 4.16 per cent of the food. * * * Diptera were contained in only 29 



