50 THE EARLY STAGES OF TABANID^ 



Chrysops moerens Walker (synonym cestuans van der Wulp). — 

 Recorded from Illinois, North Dakota, Wisconsin, and Ohio. This is 

 the species in which oviposition was first observed by Hart (1895), 

 who saw these flies from August 3 to 10 flying among the marginal 

 rushes of Fourth Lake, Sand Lake, and Slough Lake in Lake County, 

 Illinois, and ovipositing on the stems of the rushes. 



The egg is described by Hart as follows: 



"Egg. — [Plate 1, Fig. 2, egg masses.l Length 1.6 mm., diameter 0.25 mm., 

 cylindrical with rounded ends, straight or slightly curved, smooth, slightly opaque, 

 cream color when laid, becoming dark fuscous brown, placed in a single flat 

 layer, obliquely stacked as in Tahanus, about one fourth of the length of each 

 egg being visible at the surface, the remaining three fourths being covered by 

 those stacked against it. The mass is about 10 mm. long and 3 or 4 mm. wide, 

 its outline variable, usually diamond-shaped, both ends pointed, or at one end 

 short or truncate, making it more or less triangular." 



Eggs of this species were observed by Hine (1906) at Sandusky, 

 Ohio, during the first days of July and were present in varying num- 

 bers during the following two months. 



While the female is ovipositing she is not easily disturbed; conse- 

 quently one has an excellent opportunity to watch the procedure. 

 An illustration given by Hine (Plate 1, Fig. 1) was made from a 

 photograph of a living specimen which was found in the act of egg 

 laying and was carried, with the leaf, to the laboratory where the 

 picture was taken. "During the whole time," says Hine, *'she con- 

 tinued ovipositing without showing any signs that she was aware of 

 what was going on or that she had any concern for the welfare of 

 her eggs." 



The method of placing the eggs is similar to that recorded for 

 Chrysops caUidus. 



The female alights on the leaf with her head downwards and begins the process 

 by pushing the tip of the abdomen forward towards the under part of the thorax 

 and placing the protruding end of an egg against the leaf. The end sticks fast 

 in consequence of the glue-like substance which accompanies it, and she then 

 moves the tip of the abdomen back to its normal position, thus freeing the egg. 

 By similar movements one or two eggs are placed on one side of the first, and two 

 or three on the other side of it. The unfinished end soon becomes V-shaped; 

 she moves slowly forward and Hfts the tip of the abdomen to one side of the V 



