25 



1954; Hall & Kelson 1959). Its host plants are reportedly Lemaireocereiis, MyrtiUocactus 

 and Ipomea arhorea (Villa-R 1967) as well as Ceiba and Agave (Alvarez & Gonzalez 

 1970). All the results on stomach contents and the host plants identified so far (all of them 

 are specialized chiropterophiloiis night-blooming plants) convinced Alvarez & Gonzalez 

 (1970) of the fact that C. mexicana is an obligate nectar feeder. Until now, there has been 

 no evidence on insectivory. Schaldach & McLaughlin (1960) detected C. harrisoni at 

 banana blossoms {Miisa sp., therefore named the genus Musonycteris). Gardner (1977) 

 mentioned some pollen at the head and muzzle in some of the individuals having been 

 captured at a small banana plantation in Cohma, Mexico, and which had been mcluded in 

 the first description by Schaldach & McLaughlin. 



As a conclusion, all taxa mentioned here have been either proved to feed on flowers or 

 they are most probably nectar feeders. As already stated in the introduction, the short- 

 skulled forms {Glossophaga, Lionycteris) but also Anoiira frequently take insects, 

 predominantly beetles and moths. On the other hand, there is no evidence yet for 

 üisectivory in taxa with an extremely elongate skull {Choeronycteris). 



Sensory systems / Orientation 



Acoustic perception; echolocation 

 Like all Microchiroptera, the nectarivorous phyllostomatids perform an efficient 

 echolocation. Especially the nose leaf certainly contributes to sound emission. Presimiably 

 the lancet (upper part of the nose leaf) is necessary to focus the emitted soimd bundles 

 vertically (Hartley & Suthers 1987). 



Analyzing the sounds of various phyllostomid species, Griffin & Novick (1955) managed 

 to prove tliat echo location is also essential in orientation of nectar feeding bats. Furtlier 

 investigation revealed the orientation pulses of the flower bats to be frequency-modulated 

 signals of 1-5 ms lengtli (FM-sounds of the vespertiHonid type). 



Experimental investigation on tlie significance of acoustic perception in foraging was 

 performed by Howell (1974): the flower visiting species e.g. Glossophaga soricina, 

 Anoura geoffroyi and Choeronycteris mexicana emit 5-10 short searching pulses per 

 second, each of them lasting 0,5-2 ms. When approaching an obstacle (or aiming at a 

 blossom) the number of emitted orientation pulses increases to 30 signals per second, thus 

 enabling to assess distances precisely even at flight velocities of several meters per 

 second. When the bats were furtlier tested on their ability to avoid obstacles, the 

 predominantly insectivorous species complied with the abilities of other Microchiroptera 

 {My Otis), whereas the species mainly interacting with chiropterophileous plants percepted 

 only much stronger wires. Determination of acoustic perception thresholds by means of 

 shunting off the cochlea potential did not reveal any diet specific differences but indicated 

 a polyphyletic origin of the subfamily (Howell 1974). 



The importance of echolocation in pollinating bats is also documented by the development 

 of the acoustic cerebral areas (Baron & Jolicoeur 1980). Their progression indices come 

 quite close to those of insectivorous Microchiroptera. 



Optical sense 



Though in all microchiropterans a liighly developed echolocation apparatus proves 

 dominance of the acoustic system over the remaining senses, in certain situations it may 

 be replaced or complemented by optical perception. So, visual orientation becomes 



