310 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



by hovering above the less turbulent parts of the stream and dropping 

 relatively few eggs in any one place on the floating emergent vegeta- 

 tion. It deposits three to four eggs in approximately lo seconds. It is 

 difficult to find eggs if the female is not found in the process of ovi- 

 position because so few are laid in any one place. It was not realized 

 for a long time that the hovering female was ovipositing, since all other 

 species observed in this process either entered the water to deposit 

 eggs, or approached or landed on a rock or a floating leaf. The ovi- 

 position has been observed most frequently between 12:00 m. and 

 2:00 p.m. The viscous matrix covering the eggs is of cream color, 

 changing to brown and becoming harder within a few days. Within 

 3 to 10 days the young larvae emerge and soon migrate to an area 

 where the current passes over the vegetation with somewhat more 

 force. The larvae pass through four stadia, and probably a fifth, in 7 

 to 15 days. The more mature larvae maintain themselves in the swift 

 currents, but just prior to pupation they migrate to quieter sections 

 of the stream, often on the underside of the leaves or on the shielded 

 parts of stones where they are afforded more protection. Here the 

 larvae spin the cocoons in which they pupate, the process taking about 

 5 hours. The adult emerges in from 4 to 6 days and the female can 

 live at least 27 days (see "Flight Range and Longevity" in the section 

 on ecology, and Appendix III, table 32). 



SIMULIUM (5.) METALLICUM BELLAEDI 



This species is more adaptable to different types of breeding habitats 

 than is either 5*. ochraceiim or 5". callidum. Larvae are found in infant, 

 young, adolescent, and mature streams almost indiscriminately, and 

 are often found breeding in temporary streams of only a few weeks 

 duration. The breeding sites range from 350 feet to over 9,000 feet, 

 and are either open to the sun or well shaded by trees and shrubs. 

 Although the species is more commonly found breeding in regions 

 from 2,000 feet to 5,000 feet, it is not uncommonly found in areas both 

 below and above these limits. The following description of the habitat 

 will help one understand the adaptability of the species (Appendix III, 

 table 31) : 



Width: Range, i in. to > 15 ft.; optimum, i ft. to 8 ft. 



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



Temperature : Range, 8° C. to 28° C. ; optimum, 17° C. to 20° C. 



Current : Range, i in. per second to waterfalls ; optimum, i in. to 20 in. per 



second. 

 pH : Range, 6.0 to 8.0 ; optimum 6.6 to 8.0. 



