164 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



having a thermometer at his disposal, but at one place he found 

 semi-aquatic insect life close to springs and creeks the water of 

 which is close to the boiling point. The European literature on 

 the subject is very meager and like the American references only 

 proves that there are no genera or even species of true insects 

 which exclusively live in hot water, but that there are insects that 

 are very fond of living and even developing in or near hot or very 

 warm water but which are at the same time found in or near water 

 of moderate or even cold temperature. On the other hand it 

 cannot be denied that many aquatic insects are very particular 

 in the selection of their habitat as you can easily see even in the 

 vicinity of Washington. Some insects live exclusively in very 

 cold springs, others live only in the shaded, small creeks emptying 

 into the Potomac or Rock Creek; others live in the broader and 

 more sunny creeks such as the Eastern Branch, while the fauna 

 of the Potomac River and its immediate shore has many peculi- 

 arities of its own. , ' 



Knowing all this and with the expectation of not finding any- 

 thing of special interest in the creek at Castle Hot Springs in Ari- 

 zona, Mr. H. S. Barber and I visited that place at the end of June 

 in 1901. 



The little resort of Hot Springs is situated in Castle Creek can- 

 yon, Yavapai County, Arizona, near the southern end of the 

 Wickenburg Mountains at an altitude of 1970 feet. Steep and 

 high cliffs rising to about 3000 feet elevation surround the place 

 on all sides. The country is extremely arid but its scanty vege- 

 tation with its giant cactus, various other species of the same fam- 

 ily, its acacias, mesquite, etc., is not much different in general 

 aspect from that at numerous places in southern Arizona. The 

 hot springs themselves originate at the head of a little gorge about 

 150 feet above the bottom of the canyon. Where the water comes 

 out of small crevices in the solid rock its temperature is 115 

 Fahrenheit (apparently not varying throughout the year). It 

 falls then into an upper basin where the temperature is but little 

 lower than at the spring itself. This basin is surrounded by 

 steep rocks and there is no vegetation in the water except a blu- 

 ish green alga, and on the wet marginal rocks a brownish yellow 

 alga containing much calcareous matter. Thence there is a water- 

 fall of several feet and the hot water meanders as a small creek 

 over rocks and stones through the middle part of the gorge. Here 

 the temperature of the water is already considerably lower, per- 

 haps less than 100, and the creek is lined with a dense growth 

 of tall reeds, the rootlets of which, mingled with the same green 

 alga, form a swampy but quite warm breeding place for insects. 

 Arrived at the bottom of the gorge the water has (in summer- 

 time) a temperature of 94. It is used for drinking purposes, sup- 



