PARAMETERS OF COLD RESISTANCE IN EGGS OF 3 SPECIES OF GRASSHOPPERS FROM INNER-MONGOLIA

Eggs of Myrmeleotettix palpalis, Aeropedellus varigatus minutus and Da syhippus barbipes (Orthoptera, Acridoidea) comprised c.42% fresh weigh t of water, and their mean individual egg fresh weight was 3.4mg. Eggs of M. palpalis had the lowest water content (28% of fresh weight), wh ereas the other two species ranged from 46 to 52%. These were equivale nt to 0.3, 1.1 and 1.1g.g(-1) dry weight. Mean supercooling points of eggs varied little between species and ranged from -22.8 to -25.9 degr ees C although individual eggs had supercooling points of between -30. 5 and -35.0 degrees C. Three compounds (glycerol, mannitol and trehalo se) occurred in the eggs in concentrations of c.0.1% of fresh weight, insufficient to influence their supercooling potential. Thermal condit ions close to the soil surface of their steppe grassland habitat are v ery severe as temperatures below -30 degrees C occur each year in Janu ary and there is only a 3-month active period (mid-May to mid-August) for these species. The overwintering survival strategy of such eggs ma y be based an an increased capacity for supercooling enhanced by natur al dehydration in their soil surface habitat.