TABANIDiE, DESCRIPTION OF THE EARLY STAGES. 



The Tabanidae belong ecologically to the so called hydrophytic area, 

 as has been pointed out by Osburn. On the whole, they may be called 

 aquatic or semiaquatic, though not all of them pass their larval stage 

 actually in the water; at the same time they show traces of an adapta- 

 tion to plants which may serve to understand their phylogeny. The 

 larvae may be aquatic, semiaquatic, or even terrestrial in habitat, 

 but always live more or less hidden and are seldom seen. They are, 

 according to Malloch, *' found rarely among decaying leaves or in low 

 and somewhat marshy spots in fields." Neave and others, however, 

 have obtained them in quantity from the muddy banks of rivers and 

 brooks. 



The eggs are laid in clusters of one or several layers, forming a com- 

 pact fiat or conical mass; they are rarely laid scattered, and never 

 singly. The clusters may consist of several hundred eggs, the eggs 

 being held together by a sticky substance. The whole mass is often 

 covered with a dark shining varnish or with a chalky substance. 

 These masses are deposited usually on plants or sticks at the edge of 

 ponds, streams, and lakes, seldom on dry ground, and sometimes also 

 on stones above water, but this is unusual .^ The single egg is spindle- 

 shaped or cylindric, and narrowed at the ends, white, yellow, or pale 

 brownish when first laid, but later often pigmented, brown or shining 

 black, the color being due to a pigmentation of the chorion. The 

 period of incubation is short, from 3 to 9 days, but in some cases the 

 hatching process is delayed for weeks by atmospheric conditions, while 

 the embryo is fully developed and may be caused to hatch by artificial 

 stimuli. All the eggs usually hatch at the same time, the young 

 larvae at first sticking together but soon losing their hold and tumbling 

 down. In many cases only part of the eggs of one mass give birth to 

 larvae, about half of them being infected by small hymenopterous 

 parasites. ^ 



^ Macquart's statement that the female deposits its eggs in the ground is 

 erroneous. 



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