BIOLOGY OF AEIZONA WILD COTTON WEEVIL. 5 



Canyons and nearly to Oracle. The writer then crossed the range by 

 the trail above Agua Caliente Canyon, descended into the San Pedro 

 Valley on the northeastern side, and explored the slopes. Combined 

 with these observations numerous trips back and forth throughout 

 the range were made at various points which gave comparatively 

 thorough data on the internal conditions of the mountains. 



Thurberia plants were found at intervals throughout this territory. 

 Summarizing these observations it seems impossible to name any 

 certain type of situation as the normal habitat of the Thurberia plant, 

 since it is found in moist canyon beds, in dry arroyos, on dry slopes, 

 and on the top of peaks. However, by far the greater number of 

 plants are located in canyon beds, mountain washes, or arroyos 

 out through the mesa, and in searching a new locality these are usually 

 the most frequent situations in which the plant is found. Thurberia 

 plants growing under these conditions usually develop a more healthy 

 growth than those on the more exposed slopes, and usually the plants 

 at higher altitudes, on slopes and peaks, are found more or less 

 grouped in colonies. Travel for miles through such territory may 

 not disclose a single plant when suddenly colonies of from three plants 

 to several dozens are found. The distribution in canyon beds and 

 washes, however, is quite different, for here the plants are usually 

 found more or less scattered and growing singly, although in many 

 canyons a plant will be found every few yards for several miles. 

 (PL I, figs. 1, 2.) Occasionally, in locations particularly well shel- 

 tered from the force of the current, a large colony of plants may be 

 found, but such cases are infrequent. 



At lower altitudes, on the mesa and plains, Thurberia plants were 

 found extending along the dry arroyos often to a distance of several 

 miles from the base of the mountains. Here, while fairly common, 

 they are scattered, being found along the margin of the channel, on 

 small islands, or in protected situations behind rocks. 



The occurrence of the Thurberia plant at an elevation of 7,000 feet 

 was not noted until late in the season, at which time a few were 

 found on a peak at about this elevation, behind Soldiers Canyon. 

 It is interesting to> note that one specimen in the Gray Herbarium 

 and another in the Herbarium of the Academy of Sciences of Phila- 

 delphia, both collected by Edw. Palmer, bear the following data: 

 "The Frailes above Batatopas, S. W. Chihuahua, Mexico, 7000 feet 

 alt. October." 



Back in the interior of the Santa Catalina range in the small 

 canyons draining this country the plants were found to be quite 

 common along the stream beds. 



The Arizona wild-cotton weevil was found to be as widely dis- 

 tributed throughout this range as was the Thurberia plant, but the 

 weevils were by no means present on all plants. While the weevils 



