years as well. The dates encompassing the central 75% of the emergence were 6-12 July (males) 

 and 8-15 July (females). Thus, emergence of adults is quite synchronous. A total of 8.3 Pedicia 

 hannai emerged/m^ on the control plots. The male:female ratio (22:41) significantly favored fe- 

 HBles. This was in contradiction to the community gradient site, where significantly more males than 



females were captured in emergence traps. The distribution of the catch revealed a surprising de- 

 gree of within-plot, as well as between-plot, heterogeneity. The two traps on control plot 208 

 captured 21 and 1 Pedicia hannai, respectively, and the total catch per plot ranged from 3 to 25 

 individuals. The heterogeneity in adult emergence may be greater than the heterogeneity in larval 

 numbers and biomass if there is a negative association between larvae of different age (year) class- 

 es. This could produce dominant age class phenomena that are out of phase on different areas. 

 This possibility was suggested by the data on size distribution of larvae, but has not yet been sub- 

 jected to statistical test. 



The emergence of 8.3 Pedicia hannai/m' removed 0.013 g (dry weight) of biomass from the soil. 

 This is, of course, only a small part of the annual production of Pedicia hannai. Fourth instar 

 larvae, prior to pupation, weigh three to four times as much as adults; the difference is biomass 

 metabolized in pupation or cast as the final exuvium. In addition, the majority of larvae do not 

 complete pupation to emerge as adults. The biomass produced by these larvae must be considered 

 as well. A more accurate estimate of production based on changes in numbers and size distribu- 

 tion of larvae throughout the season will be made. This will be compared with estimates based 

 on metabolic rates measured at various temperatures in the laboratory. These data have yet to be 

 analyzed; however, it can be said that significant respiration occurred even at +0.5'^C, and 

 respiration rate increased sharply with increase in temperature. 



Sticky-board trapping was also used at study site 6 at which adult arthropod abundance has been 

 followed since 1967. This enables us to compare 1970 with preceding seasons. July of 1969 was 

 quite cold, and emergence of both Pedicia hannai and Tipula carinitrons was less than that recorded 

 in 1967 and 1968. In 1970 the emergence of Tipula cannilwns increased somewhat over that of 1969, 

 but was stiU below the values of 1967 and 1968. Emergence of Pedicia hannai was below even the 

 1969 value, and was the lowest recorded in the four years of observation. Thus, the estimate of 

 8.3 adults/m^ may represent a minimum figure for this species. The timing and synchrony of 

 emergence did not differ from those of previous seasons. 



Soil arthropods were sampled on the community gradient site 4 at 10-day intervals, beginning 

 on 22 June. Surface active arthropods were censused at 3-day intervals. The emergence of adult 

 Tipulidae was recorded daily throughout the period of emergence. Because of the wide range of 

 habitat conditions at this site, the sampling effort was more dispersed, and the results more subject 

 to chance variation, than on the intensive site. Still, basic patterns of distribution and abundance 

 emerged. 



Larvae of Pedicia hannai were most abundant on the wet and mesic plots, and were never found 

 on either of the two polygon top plots (5 and 6). The wettest plot (ptot 1) was also the most pro- 

 ductive for this species; more than 500 larvae/m^ occurred there on 22 June. On the community 

 gradient site, as on the intensive site, the density of Pedicia hannai showed a net decline over the 

 season. Apparently, 1970 was not a favorable year for reproduction and/ or survival of first instar 

 larvae. 



Larvae of Tipula carinitrons were found on all six of the study plots, although they were un- 

 common on the two wet tundra plots. The maximum density recorded was 180/m^ this was recorded 

 on one of the mesic plots on 22 June. 



Mites were more abundant on the two mesic plots, which resemble the plots on the intensive 

 site 2, than on the wetter or drier plots. Collembola were most numerous on the wet plots and least 

 numerous on the dry plots. In this, they resembled Pedicia hannai larvae, which prey upon Collembola. 

 However, when the numbers of Pedicia hannai and Collembola from individual samples were analyzed 



47 



