RESISTANCE OF THE EGGS OF STEGOMYIA FASCIATA. 85 



Fig. 3 shows eggs from the same batch as the foregoing, removed from the water 

 3| days later. They were allowed to dry on filter-paper in the same way, and were 

 photographed 12 hours after they were thoroughly dry. These eggs, moreover, while 

 being photographed, were exposed to the condensed beam of an electric arc light 

 for over an hour, with neither heat nor colour screens interposed, and were thus 

 subjected to considerable heating. Both sets of eggs after they had been photo- 

 graphed were separately brushed into glass tubes, to each of which water was added. 

 The collapsed eggs failed to hatch, but the normal-looking eggs (fig. 3) notwithstanding 

 having been subjected to desiccation, considerable heat, and intense hght, hatched out 

 six hours later active larvae that developed normally into imagos of normal size. 



Remarks. — The resistance of the eggs of S. fasciata to desiccation is only attained 

 after the eggs have been in contact with water for some time, and with the definite 

 results that I have had in these experiments, my former conviction that the partially 

 collapsed eggs from West Africa had also hatched out is probably incorrect. A larger 

 number of normal-looking (i.e., resistant) eggs than were visible on the leaves may 

 have been present buried in the mud deposit previously mentioned, and these would 

 account for the surprisingly large number of larvae that were hatched. 



The embryos of freshly laid eggs are very easily Irilled by drying, and if such eggs 

 are removed from water only long enough for the first evidences of the shell collapse 

 to appear, and are then replaced on water, it has been found that they fail to develop. 



Naturally laboratory experiments cannot altogether simulate conditions in nature, 

 and the degree of humidity of the atmosphere in certain tropical places may play an 

 important role in allowng even freshly laid eggs when removed from the water to 

 develop their resistant powers, but the fact is demonstrated at least that these eggs 

 are particularly liable to destruction by desiccation. 



