312 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 12$ 



(see "Flight Range and Longevity" in the section on ecology, and 

 Appendix III, table 32). 



SIMULIUM (L.) CALLIDUM (dYAR AND SHANNON) 



Although neither the pupae nor the adults of this species are found 

 in large concentrations, it seems to have adapted itself to many differ- 

 ent types of streams far better than S. ochraceum. It has been found 

 breeding primarily in streams similar to those in which .9. metallicmn 

 is found. Its unique oviposition habits and the migration of its larvae 

 have made it difficult to study the life history of this species. The 

 streams in which S. callidmn are found are usually in regions not very 

 heavily wooded, and such streams are only lightly shaded by trees and 

 shrubs, if at all. They are invariably more accessible than the breeding 

 places of 5. ochraceum. The altitudes at which 5. callidiim has been 

 taken are from 900 to 8,200 feet, but usually between 900 to 6,000 feet. 

 The streams can be characterized as follows (Appendix III, table 31) : 



Width: Range, i in. to >I5 ft.; optimum, i ft. to 15 ft. 



Depth: Range, <i in. to >3 ft.; optimum, i in. to i ft. 



Temperature : Range, 9° C. to 25° C. ; optimum, 17° C. to 20° C. 



Current: Range, i in. per second to waterfalls; optimum, I in. to 30 in. per 



second. 

 pH : Range, <6.o to >8.o; optimum, 6.6 to 8.0. 



The eggs, larvae, and pupae have been found on the following 

 plants : 



Axonopus compressus (Sw.) Beauv. Renealmia sp. 



Coix lachryma-jobi L. Ipomoea sp. 



Tradescantia commelinoides R. and S. Hyptis sintiata Pohl 



Tradescantia guatemalensis C. B. Clarke Leguminosae 

 Tripoga'udra cumanensis (Kunth) Woodson 



Other species commonly found breeding (in order of frequency) in 

 the same streams as .S". callidum are (Appendix III, table 2)?)) '• 



S. metallicum S. veracrusanmn S. acatenangoensis 



S. rubicundulum S. smarti S. jacumbae 



S. downsi S. jobbhisi S. pulverulentum 



S. mexicanum S. capricornis S. parrai 



S. ochraceum S. exiguum S. yepocapense 



The mating, egg development, and fertilization of 5. callidum is 

 similar to that of the two other species just discussed. The females 

 have been seen ovipositing only on sharply inclined surfaces of rocks 

 and stones in parts of the stream where the current is not very strong, 

 but where the water definitely flows over the eggs. The most usual 

 hours were from 3 130 p.m. to 5 :30 p.m. The female hovers above the 



