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THE NATIONAL GEOGRAPHIC MAGAZINE 



son, Arizona, I once saw them, a short time 

 before dark, issuing from a small window in 

 the gable of a church in such numbers that in 

 the half light they gave the appearance of 

 smoke pouring out of the opening. At times 

 they occupy houses in such numbers that their 

 presence and accompanying offensive odor ren- 

 der the places uninhabitable. At the town of 

 Patzcuaro, near the southern end of the Mexi- 

 can table-land, I saw two rooms in an old 

 adobe house occupied by as many of them as 

 could possibly hang from the rough ceiling. 

 The owner considered their presence a valuable 

 asset, as he collected and sold the guano for 

 more than the rooms would have brought in 

 rent. The bats congregate in even greater num- 

 bers in large caves. So numerous are they in 

 certain caves in Texas that the owner reports 

 an annual income of about $7,000 from the 

 guano. 



They are very plentiful by day in the thin 

 crevices about the roof and walls of caves in 

 the celebrated Ixtapalapa, or "Hill of the Star," 

 beyond the floating gardens at the City of 

 Mexico, and I also found them living in many 

 of the marvelous ruins of Mexico, including 

 Chichen-Itza, in Yucatan. Wherever they occur 

 in numbers they may be heard frequently by 

 day shuffling uneasily about and squeaking 

 shrilly at one another. 



When they first come out after sunset they 

 usually fly away in a great stream, nearly all 

 in the same direction, as though migrating. 

 This course will probably be found leading to 

 water, where they scoop up a drink from the 

 surface before beginning their wonderfully er- 

 ratic zigzags through the air in pursuit of in- 

 sects. 



From the colder northern parts of their range 

 they migrate southward to milder climatic con- 

 ditions or descend to lower altitudes. In Mex- 

 ico, where they live up to above 8,000 feet alti- 

 tude, they move down from one to two thousand 

 feet. Their young, one at a birth, are born 

 from April to May. 



It has been claimed that the Mexican bat 

 brings bedbugs to infest houses. This is un- 

 true of this or any other bat. These animals 

 have certain small parasites, some of which, re- 

 sembling small bedbugs, have probably given 

 rise to the belief mentioned. These parasites 

 live only on the bats. 



Within a few years considerable publicity has 

 been given to the supposed possibility of utilizing 

 bats to destroy mosquitoes and thus eliminate 

 malaria from infested areas. One or more bat 

 houses have been built at San Antonio, Texas, 

 for the purpose of assembling bats in large 

 numbers, and many untenable claims have been 

 put forth concerning the benefit to be derived 

 from their services. The Mexican bat is the 

 species which abounds above all others at San 

 Antonio and is the principal species which has 

 occupied the bat houses near town. It is def- 

 initely known that bats often fly miles from 

 their roosts when feeding and do not concen- 

 trate on any one kind of insect. Examination 

 of the contents of the stomachs of Mexican bats 

 shows that they feed on beetles and numerous 



other insects, but rarely upon mosquitoes. I 

 have \- i > i t c ( 1 many Mexican towns and villages 

 in which every house was haunted by numbers 

 of these bats and where malaria was perennial. 

 The evidence .against these animals serving any 

 useful purpose in checking malaria is con- 

 clusive. 



It may be repeated here, however, that all 

 of our bats are of lv'gh utility as insect-destroy- 

 ers and should he protected. Among the many 

 species of varying habits which exist in the 

 United States, a few make their homes about 

 houses in annoying numbers. In place of killing 

 them to abate the nuisance, it would be better 

 to exclude them from buildings by closing the 

 entrance ways promptly after all have left in 

 the evening, and thus by quiet eviction cause 

 them to find abiding places elsewhere. The 

 destruction of forests, and the consequent ab- 

 sence of the hollow trees where they formerly 

 lived, is mainly responsible for bats and chim- 

 ney swifts coming to houses for harbor. 



THE BIG-EARED DESERT BAT (An- 

 trozous pallidus and its relatives) 



{For illustration, see page 465) 



The marvelous variations in structure of the 

 ears and other organs about the heads of insect- 

 eating bats serve probably as microphones by 

 which the flight of their prey may be detected 

 and its direction located with instantaneous 

 certainty. The beautiful accuracy with which 

 this hearing mechanism works must be evident 

 to any one who will take a position where he 

 may have the evening glow of the western sky 

 as_ a background for flights of bats. It is cer- 

 tain that the small and ineffective eyes these 

 animals possess could never locate their minute 

 flying game and enable them to secure it in 

 the whirling, zigzag courses they pursue, often 

 at a speed and under a control which few, if 

 any, birds could rival. 



The great ears of the big-eared desert bats 

 illustrate one form of a highly developed hear- 

 ing apparatus and give these animals a hand- 

 some and strikingly picturesque appearance. 

 This character at once distinguishes them from 

 others of their kind in the United States. 



The distribution of this species lies mainly in 

 the arid parts of the Southwestern States and 

 Mexico. It extends from western Texas, south- 

 ern Colorado, Nevada, and Oregon, south to 

 Queretaro, on the Mexican table-land, and to 

 the southern end of the peninsula of Lower 

 California. The vertical distribution extends 

 from sea-level up to at least 5,000 feet altitude. 



By day these desert bats live in crevices and 

 caves in cliffs, in old mining tunnels, hollows 

 in trees, and in sheltered places about the roofs 

 and walls of houses, barns, or other buildings. 

 Their presence in dark hiding places may some- 

 times be detected by occasional grating squeaks. 

 They appear to lack any musky odor which 

 characterizes so many bats. About the 1st of 

 June each year either one or two young are 

 born, and for a time these cling to the mother's 



