Submitted to: Journal of Orthoptera Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2011
Publication Date: 8/20/2011
Citation: Fielding, D.J. 2011. Oviposition site selection by the grasshoppers Melanoplus borealis and M. sanguinipes (Orthoptera: Acrididae). Journal of Orthoptera Research. 20:75-80.
Interpretive Summary: Grasshoppers lay their eggs in the ground and are selective with respect to the soil conditions where they place their eggs. Temperature and moisture are important parameters in site selection for egg laying. In this paper, two common species of grasshopper from the subarctic region are examined to discover the range of temperatures preferred for oviposition. A population of one species from temperate regions was also included in experiments for comparative purposes. Grasshoppers preferred to lay their eggs in moist sand at a temperature range of 28 to 40 degrees C. When grasshoppers were limited to a choice of cool, moist sand or dry, warm sand, they preferred the moist sand at temperatures of 15 degrees C or warmer. Otherwise, oviposition was curtailed or they laid their eggs in the dry sand. In field cages, they preferred to lay eggs in bare ground rather than sod. These results suggest that establishment of thick stands of grass may reduce egg laying by these grasshoppers and represents an long-term, environmentally sound method of limiting pest grasshopper populations.
Technical Abstract: Female grasshoppers can affect the fitness of their offspring through their selection of oviposition sites. Successful embryological development depends on suitable temperature and moisture levels, factors which may vary considerably on a fine scale in natural environments where grasshoppers occur. Knowledge of the parameters defining acceptable oviposition sites can provide guidelines for habitat manipulations that reduce the availability of acceptable oviposition sites. This paper compares oviposition site selection in two species of grasshopper from Alaska, Melanoplus borealis and M. sanguinipes, and a population of M.sanguinipes from Idaho. Laboratory experiments did not detect any differences in preferred substrate temperature among the groups of grasshoppers. In field cages containing a choice of different ground covers (bare ground, single clump of grass, or turf), M. sanguinipes from Idaho were less selective in terms of the distribution of eggs pods among the different cover types, whereas both M. borealis and M. sanguinipes from Alaska deposited the fewest egg pods under the turf. Results suggest that differences in oviposition behavior between the grasshoppers from Idaho and from Alaska may stem more from differences in the above-ground physical structure of the vegetation, than from differences in below-ground temperatures.