Seasonal Weight and Total Water Content of the Mound‐Building Ant, Formica Exsectoides Forel

Abstract

The body water content of several insects has been shown to have significance in relation to cold hardiness, starvation and rate of metabolism at different temperatures and humidities. These observations, while interrelated, are neither uniform in their findings nor properly coordinated. For instance, using determinations of freezing point or undercooling point and blood conductivity as criteria for measuring the water content of tissues, Payne ('26 and '28) has shown that oak borers, larvae of Synchroa and Dendroides, and larvae of the Japanese beetle, Popillia japonica, undergo dehydration when subjected to low temperature or low humidity. This condition is associated with increased cold hardiness. Robinson ('28a and '28b) has shown that in proinethlea pupae (Callosamtia pronlethea) and white grubs (Phyllophaga) there is no change in total water content when the animals are subjected to low temperatures. In the case of the pronmethea pupae, however, there is a decrease in the percentage of free water in the tissues during the first two weeks of exposure accompanied by a corresponding increase in the percentage of bound water. He associates this change with increased cold survival. Buxton ('30 and '32) and Mellanby ('32a and '32b) concluded that starving mealworms (Tenebrio molitor), bedbugs (Cimex lectularius) and blood-sucking bugs (Rhodnius prolixus) regulate their rate of metabolism to maintain a constant percentage of water in the body at certain temperatures and humidities to which they are adapted. Both of these conditions, survival of low temperature and regulation of body water in relation to metabolism at different temperatures and humidities, are significant aspects of the problem of adjustment to seasonal temperature as in hibernation. Other investigators, such as Tower ('06), Baumberger ('14), Bodine ('21 and '23) and Fink ('25), have described a decrease in the body water content of various hibernating insects, e.g. the potato beetle, codling moth, and grasshoppers. Bodine ('21 and '23), Fink ('25), Payne ('28) and Kleinman ('34) have reported a decrease in the volume of respiratory exchange and a lowering of the respiratory quotient associated with low temperature during hibernation. In a previous publication (Dreyer, '32) it was shown that the rate of metabolism of the mound-building ant, Formilca ulkei, is greatly altered dur38