MOSQUITO BIOLOGY 47 



they were allowed to dry. September 23, when these eggs were again 

 covered with water they hatched freely. Eggs that had been kept dry 

 since laid were covered with water September 5, and hatched. Eggs kept 

 under similar conditions, one series on marsh mud, the other on upland 

 soil, were covered with water September 30. Five hours later wrigglers 

 were found over the marsh mud ; but three days later none had yet ap- 

 peared over the upland soil ! 



In one case a number of gravid females were caught in a net with a 

 mass of other material. This was all placed in a jar and the mosquitoes 

 began ovipositing at once, in masses. Only a few of the eggs had turned 

 black twenty-four hours later when they were covered with water. A 

 small number of these black eggs hatched; all of the white examples 

 collapsed. 



Some other experiments were made and from those as well as from 

 the above record, Mr, Viereck concludes as follows : No black eggs were 

 laid and only one specimen was found with black eggs in it. All eggs 

 laid outdoors (presumably) and in the experiment jars (certainly) 

 were white when laid. They changed from white to steel color and then 

 to black, gradually, in one hour and a half. Eggs were laid on moist 

 material, but not in water, nor on dry sand or lint. Some hatched 

 overnight when the fresh eggs were covered after having turned black ; 

 but usually they did not hatch until two or three days had intervened 

 before they were covered with water. One lot placed under water did 

 not hatch in weeks ; these eggs when dried and again covered with water, 

 did hatch. In one jar several hatchings took place at intervals of three 

 days. Eggs kept indoors and exposed to the air of the room collapsed. 

 Eggs under the influence of the moisture of a closet did not collapse 

 when in the mold of black grass marsh, but did collapse when the mate- 

 rial was ordinary garden soil or lint. Eggs hatched in all percentages of 

 sea water, their further progress depending on food. Larvae died in 

 water at 40°C. (103°F,) ; they survived at 37°C. (98°F,), Mr. Viereck 

 is further of the opinion that whether the eggs will collapse or not after 

 being laid, depends also on the stage of development when they are laid : 

 thus, those fully developed remain entire, while those not so mature, 

 such as the ones laid by an injured female, need moisture to develop 

 them further. 



The general statement here made is undoubtedly correct, but it 

 should be added that the records indicate that the eggs laid under such 

 stress as Mr. Viereck indicates are not fertilized, and, therefore, not 

 viable in any event. It should be further noted that the apparent differ- 

 ence between Mr, Viereck and myself concerning the color of the eggs 



