Septembek 5, 1902.] 



SCIENCE. 



393 



ing 117 larvse were counted and some of these 

 were carried to maturity, so that the complete 

 life cycle from egg to adult was under observa- 

 tion. 



August 10, duplicated this experiment but 

 began about 8 a.m., to determine the time of 

 the appearance of the first larvs. Before 10 

 A.M. the dish was swarming with wigglers ; 

 all the eggs had hatched in less than two hours. 



On the same day I cut oif a small section of 

 the sod that had been kept continuously moist 

 and washed this into a dish. Twenty-four 

 hours later no larvae had developed and I sub- 

 mitted the mud to close examination. Nu- 

 merous eggs and egg fragments were found, 

 making it certain that the absence of larvse 

 was not the natural result of the absence of 

 eggs. 



August 11, this last experiment was dupli- 

 cated with the same result. The sod had been 

 so wet as to induce development and perhaps 

 hatching while there was no water to support 

 the larva. The latter suggestion is due to the 

 large number of broken eggs that were found. 



August 12, Mr. Dickerson washed the mud 

 from a small square of dry sod into a large 

 dish and began transferring the eggs into a 

 watch glass. It was a slow job because the 

 black eggs are not readily differentiated from 

 the black mud, and in about half an hour he 

 began to find broken eggs. Transferring the 

 watch glass from a white to a black backing he 

 saw several pure white, minute wigglers, just 

 out of the egg. Half an hour's submergence, 

 then, was enough to start out the larvse, and 

 soon afterward it became impossible to find un- 

 broken eggs. The piece of washed sod was 

 placed in another dish and, an hour later, more 

 larvae were obtained. When the larva is ready 

 to emerge, about one fourth of the egg lifts 

 or breaks off, giving it exit. The small end 

 may remain attached to the larger for a time 

 by a sort of hinge; but it is detached by the 

 least shaking of the water. 



We have then, briefly, the following life his- 

 tory. The adult lays eggs, singly, in the mud 

 of salt meadows above ordinary high tide 

 and where the sod is not soaking wet. It 

 probably lays them elsewhere as well, but I 

 am stating the uule, as I believe. The eggs 



remain here an unknown length of time until 

 an extra tide or a heavy rain covers them with 

 water. The eggs hatch almost immediately 

 and the larvse find their food in the soft, de- 

 composing mud. It makes little diilerence 

 whether the water is fresh or salt, so long as 

 the proper food is present. The stay in the 

 larval and pupal condition varies according to 

 temperature, but is not less than a week. The 

 males emerge fijst and rarely, if ever, leave the 

 immediate vicinity of the place of hatching. 

 It is probable that copulation takes places soon 

 after the female emerges, but I have made no 

 direct observations, and have been unable to 

 secure a pairing in captivity. It is also prob- 

 able that the females do not fly to any distance 

 until they have been impregnated and it is cer- 

 tain that there is no development of the eggs 

 until the insect has fed. A long series of 

 specimens collected as they came to the attack 

 and afterward dissected, all showed an empty 

 alimentary canal and undeveloped ovaries. 

 Another series, collected by sweeping in the 

 natural breeding places showed that wherever 

 the ovaries were developing the alimentary 

 canal showed food remnants, greater or less, 

 according as the eggs were undersized or 

 approaching maturity. When the eggs were 

 fully developed the food remnants disappeared. 

 So far as determined the food was blood in 

 aU cases ; but of what kind was not made out. 

 As the collections were made near a settlement, 

 it might have been of horse, cow, dog or man. 



I have already referred to ttle specimens 

 sent on July 15. On the 20th I collected a lot 

 of about 100 examples by sweeping, and ex- 

 amined for ova. Curiously enough, none of 

 the examples had fully developed eggs. They 

 ran all the way to full size, beginning to turn 

 translucent as the shell became differentiated; 

 but not a black egg was found. The number 

 of eggs varied greatly, but rarely reached 200 

 and rarely fell below 125. 



Not all the points of interest in the life cycle 

 of the insect are covered, but enough is now 

 known to understand the economic problem. 

 We know that, so far as this species is con- 

 cerned, all permanent water areas, deep or 

 shallow, are safe. So are temporary pools in 

 very wet salt meadows. AU meadows covered 



