Development, Survival and Reproduction of Camnula pellucida (Scudder) (Orthoptera: Acrididae) in Relation to Climatic Conditions

Abstract

Field-rearing studies of Camnula pellucida (Scudder) conducted at Saskatoon from 1960 to 1962 indicated that marked differences often occurred in rate of development, survival and fecundity because of differing weather patterns. Grasshoppers usually developed more rapidly as they hatched later in the season when temperatures were rising. In addition, striking differences occurred in growth rates of grasshoppers hatched on similar dates in different years due to sharply contrasting climatic conditions. Although survival of nymphs was generally high, mortality was consistently greatest during early nymphal life. Precipitation or excessively hot weather during this period increased mortality considerably, yet did not affect the older nymphs. Survival of adults was also generally high whether they fledged early or late in the season. They were able to endure very high temperatures during mid-summer or below freezing temperatures during late autumn. The three-year average reproductive capacity of this grasshopper was approximately eight egg-pods or 176 eggs per female. The rate of oviposition varied with temperature, reaching a maximum per female of approximately one pod every four days during mid-summer when temperatures were high and declining thereafter as temperatures dropped. The average egg-pod contained 22.13 eggs which showed a tendency to increase as adults fledged later in the season.It is suggested that climatic conditions frequently play a decisive role in the short-term modification of grasshopper infestations as well as in the long-term cyclic rise and fall in populations; consistently favourable or unfavourable conditions throughout the grasshopper cycle could result in an explosive outbreak or in almost complete elimination of any threat to the crop.