Prokelesia marginata Van Duzee (Homoptera: Fulgoridae), which occurs the 

 year round, but is most common in winter. The Orchelimum population was 

 sampled with a sweep net, and density on an area basis estimated by a modi- 

 fication of the method of G. Beall (Ecol. , 16^:216-225), Prokelesia density 

 was estimated by cutting off grass in a quadrat of known area and placing the 

 grass and insects into preservative (this could be done without disturbing the 

 insects); or by placing a paper bag quickly over some grass and introducing 

 some paradichlorobenzene into the bag. 



In order to equate the organisms which differed widely in size, life history 

 and rate of metabolism, energy flow was used as a basis for comparison 

 (Table 1). Energy flow is defined as the total population assimilation rate 

 which is the sum of the respiration of the standing crop and the production of 

 new biomass per unit time. Respiration per gram at the temperatures of the 

 natural environment was calculated from oxygen consumption-temperature 

 curves of different stages as determined in the laboratory. Respiration was 

 converted to Calories by the oxycaloric coefficient of V. Ivlev (Biochem. 

 Ztschr, , 275 ;49-55). Production was calculated for Orchelimum by finding 

 mortality from a survivorship curve constructed from periodic population 

 samples. The sum of the caloric content (from bomb calorimetry) of the 

 grasshoppers dying in each sample period equals the total production, since 

 none of them survive to overwinter. The production of Prokelesia was found 

 by assuming a ratio of respiration/assimilation of 75 percent, which is ap- 

 proximately true for a wide variety of animals (H. T. Odum, Ecol. Monogr. , 

 27:55-112, J. M. Teal, ibid. , 27:283-302). 



As may be seen from Table 1, the two major herbivores assimilate only 

 7 percent of the annual net production of grass. In comparison, the "utilization 

 efficiency" of herbivores is 38 percent (Odum, op. crt. ) in a spring community 

 and as high as 81 percent in a marine zooplankton-phytoplankton system in the 

 English Channel (H. Harvey, J. Mar. Biol. Assoc. U. K. , 29:97-137). It is 

 suggested that a tidal marsh is similar to a forest in its trophic structure at 

 the herbivore level, since in either case immediate consumption of the primary 

 photosynthetic product is of less importance than its subsequent utilization and 

 decomposition by detritus feeders and microorganisms. 



Table 1 . 

 Production and standing crop consumption oi Spartina in KC/m /yr. 



~~~ Orchelimum Prokeles ia Spartina 



fidicinium marginata alterniflora 



Energy Utilization (Respiration) 14 205 



Production 11 69 4248 (net) 



Assimilation (Energy Flow) 25 274 



TT^-T .-■ TT^ff • i-u^ \ Assimilation of Herbivores _ n 07 ot 7% 



Utilization Efficiency (En) : : U.U/ or i /o 



Net Spartina production 



97 



