12 



Bacteria and Insect Eggs . Atkin and Bacot (1917) a nd 

 Bacot (1917) found that the greatest stimulus to the 

 hatching of mosquito eggs ( Stegomyia faciata ) was the 

 introduction into their environment of living yeasts or 

 "bacteria. The stimulus produced "by killed cultures of 

 "bacteria and sterile watery extracts of brewer's yeast 

 was more feeble, many of the eggs failing to hatch. 

 Sterile filtrates of "bacteria were less effective than 

 killed cultures. The methods of experimentation were 

 simple. Different species of living "bacteria were intro- 

 duced into tubes of sterile media, such as peptone water, 

 in which the eggs had "been lying dormant for 11 to 15, 

 and in some cases, 39 days. Upon inoculation with the 

 "bacteria all eggs hatched within 18 hours. Atkin and 

 Bacot explain this phenomenon "by supposing that the 

 stimulus is of the nature of a "scent" which penetrates 

 to the larvae lying dormant within the egg shells, causing 

 them to make vigorous movements which result in the un- 

 capping of the egg. 



On the other hand, Barter (1928) found "there was no 

 indication that "bacteria promoted hatching in either C. 

 [CuLex] quinquefasciatus or A. [ Aedes 1 aegypti . Eggs 

 hatched out in water or in clear sterile media as promptly 

 as in contaminated cultures. In a few cases bacteria 

 seemed to encourage the hatching of eggs of A. [Aedes] 

 sollicitans , "but they were surely not a necessary stimulus." 

 Similarly, Hinman (1930 obtained results which were in 

 direct opposition to those of Atkin and Bacot. Hinman 

 "repeatedly found that eggs of this mosquito [ Aedes 

 aegypti ] (and also other species) hatched apparently as 

 rapidly in sterile as in contaminated media. " 



Some of the differences of opinion on this phenomenon 

 were reconciled by Rozeboom (193*0, who found that a great 

 deal depends on the age and condition of the egg. Of 2^0 

 old, dry eggs ( Aedes aegypti ) only four hatched in sterile 

 media, whereas 20^ hatched within two days following 

 inoculation of the media with bacteria. Of fresh, moist 

 eggs, 35 per cent hatched in distilled water, and 82 per 

 cent in water contaminated with "bacteria. 



More recently Gjullin, Yates, and Stage (1939) founa 

 that tap-water infusions of dry cottonwood leaves, willow 

 leaves and grass gave consistently larger hatches of 

 Aedes vexans and Aedes aldrichi eggs than either tap or 

 river water alone. They concluded that the amino acids 

 and proteins present in vegetation may "be the stimulants 

 which cause the eggs to hatch when flooded in nature. 



