Author
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Fisher, James |
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Submitted to: Entomology Society Of America Annals
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/2/1994 Publication Date: N/A Citation: N/A Interpretive Summary: Modern control of insects such as grasshoppers requires extensive knowledge about the life functions of the target species. Life functions start with the process of birth or with insects, eggs. We have successfully modeled the growth process of some grasshopper species after egg hatch but the efficiency of those models in forecasting for proper timing of biological, chemical or cultural controls is hindered by the lack of knowledge of egg development and the timing of egg hatch. This study fills that gap of knowledge for three of the most economically damaging species of grasshoppers in the USA: Melanoplus sanguinipes, the lesser migratory grasshopper; Melanoplus bivittatus, the two-stripped grasshopper; and Melanoplus differentialis, the differential grasshopper. With all species, rate of development increased and thus, the number of days to hatch decreased as incubation temperatures rose from 22 to 40 degrees C, but mortality increased at temperatures between 36 to 40 degrees C. Mortality came quickly and absolute when eggs of all species were incubated at temperatures equal to or less than 42 degrees C. This study provides insight as to why these three species are detected at different times in the late spring- early summer and offers optimal temperature regimes for incubating eggs for those interested in rearing these species. Technical Abstract: Post-diapause development and survival of embryos to hatch were studied at ten constant temperatures (12, 15, 18, 24, 27, 30, 33, 36, 39, and 42 degrees C) for three species of North American grasshoppers: Melanoplus sanguinipes (F.), M. bivittatus (Say) and M. differentialis (Thomas). Methods used in this study allowed for determination of: (1) rate of development per day per temperature regime, (2) first day of hatch, (3) mean days to hatch, (4) an estimate of the thermal accumulations needed for hatch at each temperature regime, (5) an estimate of the minimum and maximum thermal limits for egg development, and (6) the optimal temperature range and the optimum temperature for post-diapause egg development. Melanoplus sanguinipes and M. bivittatus had similar development curves (rate vs temperature) with developmental thresholds of 10.4 and 9.8 degrees C, respectively. M. differentialis had a different and slower development curve but the developmental threshold was 8.8 degrees C. Even though M. differentialis had a lower developmental threshold, mean hatch days and the time to the first day of hatch and the respective thermal units were nearly double that of either M. sanguinipes or M. bivittatus. Percent hatch was greatest at 26.8 degrees C for M. sanguinipes, 24 degrees C for M. bivittatus and 26.3 degrees C for M. differentialis; thermal death points were reached at 43, 42 and 42.3 degrees C, respectively. This study, being the first to span the complete range of viable temperatures for the eggs of these species, offers valuable information for rearing these species and contributes to the understanding of hatch and occurrence of these species in northwestern U.S.A. |
