10 



CROP PEST COMMISSION OP 



The black horsefly* is very apt to place its large mass of 



, containing upwards of 500, in a certain position on a par- 

 ticular species of sedge in low ground near swamps and ponds. 



The rather small horsefly known as Chrysops callidus ar- 

 ra nr's her eggs in a single layer on leaves of various kinds of 

 plants overhanging the water of ponds and small lakes. 



(li-rysops moerens oviposits much like the last, except that 

 tlir eurirs arc placed over deeper water. Tt is not rare to find 



Fi<;. .'{.Eggs of an earfly, Chrysops moerens, enlarged. 

 (After Hart, Bull. Ills. State Lab., Volume IV.) 



these e.ggs on giant sedges standing in four or five feet of water. 

 The eggs when first laid are white in the case of all species 

 thus far observed, but gradually get darker until they become 

 blown or black. The eggs of the various species of Ckrysops 

 are usually shining black, while those of Tdbanus are more often 

 clear brown. Thus we see that since the eggs of horseflies are 

 laid on a green surface they form a striking contrast with their 

 surroundings. 



It is well known that in some of the flesh-flies or scavengers, 

 the eggs are either hatched, or nearly ready to hatch, when 

 tU-positiori takes place. Not so with eggs of the horseflies, for 

 these do not show any apparent development when first laid ; and 

 as about seven days are required for them to hatch under fa- 

 rorable conditions, we are safe in concluding that incubation 

 has not advanced far at the time of laying. It is very interest- 

 ing to watch a brood of these minute larvae leave the eggs, for 



'Tabunun atratu/t. 



