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Bulletin American Museum of Natural History. [Vol. XXXVII, 



At this particular spot only adult males assembled, as was shown by the 

 nine specimens shot as they crossed the river; before darkness set in they 

 had all arrived. Yet they did not seem to come in search of food. Large 

 rat-traps baited with guavas were fastened in the trees they visited, but none 

 was touched. 



Just before they began to cross the stream, every evening, we could hear 

 the whole chorus far back in the forest, where they evidently spent the day 

 with their females and young. An overcast sky would delay their arrival 

 10 or 15 minutes, and rain would practically silence them. Although 

 wounded females have been heard to produce a harsh noise, the old males 

 alone call in this loud fashion. Their enormous ossified larynx is responsible 

 for their very loud voice. The males of Epomops franqucti, which likewise 

 call strenuously, also show an enlargement of this organ, whereas the 

 females of both species have it more moderately developed. In Epo- 

 mophorus anurus and Eidolon helvum, on the other hand, species which are 

 comparatively silent, the larynx is of normal size. 



We observed the hammer-headed bat in the northeastern part of the 

 Congo forest throughout the year, and we are sure it does not migrate; 

 yet there is no doubt that the ripening of certain fruits, wild and cultivated, 

 influence its local occurrence. 



At the post of Avakubi throughout the following May and early June 

 (1914), many hammer-headed bats were to be seen flying about every even- 

 ing, making their appearance about a quarter of an hour after sundown. 

 They turned their attention at once to the guava trees, fluttering and 

 hovering in search of fruit. They were awkward at plucking the guavas, 

 which are undoubtedly taken in the mouth, for one of them killed by a rat- 

 trap was still clasping the fruit in its teeth. Next the fruit was carried off 

 to some convenient perch — usually bare of foliage, often in a mango tree — 

 perhaps 100 yards away, where they proceeded to cut it up with the teeth, 

 letting drop a great deal of the pulp and probably swallowing simply the soft- 

 est parts, perhaps only the juice. The elliptical rasp-like patch on the upper 

 surface of the long tongue helps in these operations (Text Fig. 16, p. 485). 



So numerous were the bats at this time that spots covered with guava 

 pulp and half-eaten guavas were to be seen on the ground all about the 

 station. Mangos, too, were now ripening, but they were only occasionally 

 consumed. Other fruits known to be devoured by this bat are wild figs, 

 sour sop, and bananas. 



Contrary to what we had observed up the river, these bats were mostly 

 immature; but there were a few adult males among them whose voices were 

 sometimes heard. During the day stragglers were found hanging in shady 

 mango trees about the station, but the majority went somewhere else to 

 roost. By the end of June their visits had ceased. 



