HABITS AND LIFE HISTORIES OF TABANIDyE. 29 



observed, onh' a very few were placed on other species of plants or in 

 a different position on the leaf (tig-. 5). The female (tig. 6) is occupied 

 for a half hour or more in placing the several hundred eggs composing 

 a single mass, and during this time the observer can take a position 

 close by and watch the proceedings without frightening her away, 

 but species of Taiwan us are more particular about the approach of 

 intruders than are various Chr3'.sops. 



/ The egg mass (tigs. 4, 5) is white when first placed but turns brown 

 shortly; it is ver}^ convex, and is composed of about live laj^ers, one 

 above the other. Individual eggs are of nearly the same size as those 



Fig. 4.— Eggs of Tabanus sti/f/iits, showing the location, with relY'rence to the leaf, in which they are 

 usually found. From a photograph; reduced (original). 



of the black horsefly {Tahanus ati'atux Fab.), and are similar to them 

 in form. Hatching, as observed, occurred in seven days after ovi- 

 position. From a careful stud}' of microscopic sections of eggs killed 

 as soon as laid it was concluded that development does not begin until 

 after oviposition, consequently the time given is the entire incubation 

 period. 



When first hatched the larvic contain a considerable amount of 

 unused yolk, which furnishes them food for a time; it is therefore 

 unnecessar}" for them to eat anything for a few daN's. This is advan- 

 tageous no doubt, for food is not always just at hand, and in case it is 



