388 



THE MONTHLY BULLETIN. 



THE EGG. 



The egg of Cryptochaetuiii is very minute, averaging about .3 mm. in 

 length. It is oblong oval in shape, slightly wider at one end than at 



the other, pearly white in color and without 

 visible sculpture. Owing to the difficulty of 

 getting the flies to oviposit in confinement we 

 have been unable to ascertain just how long the 

 egg stage lasts, but indications are that it 

 hatches in about four or five days. The eggs 

 are quite numerous and it is probable that a 

 single female deposits as high as 200 eggs. On 

 the dissection of the adult insect we frequently 

 find as high as 120 mature eggs in the ovarian 

 tubes. 



Fig. 132.— The egg. 

 Greatly enlarged. 

 (Original.) 



THE YOUNG LARVA. 



The young larva is a very curious creature, as will be seen by the 

 accompanying illustration. It is found swimming about freely in the 

 body cavity and at this stage apparently does not inconvenience its 

 host in the least. The most conspicuous anatomical feature consists 

 of the two long tails which are sometimes twice the length of the 

 body. The larva is semitransparent with a conspicuous black mouth- 



'^^^^ 



\ 



Fig. 133. — The young larva. Greatly enlarged. (Original.) 



hook. This mouth-hook consists of three pieces, as will be seen in the 

 accompanying figure. The large posterior section, provided with two 

 dorsal projections, is apparently useful in the main as a place for mus- 

 cular attachment. The two "jaws" just anterior to this function in 

 the taking in of food, and since in this stage no tissue of the host is 

 destroyed, they probably serve to produce a current of the juices of 

 the host toward the interior of the parasite. In living larvae they are 

 continually opening and closing like a pair of jaws. The anterior 

 half of the larva is smooth, with sutures visible, 

 however. The posterior half has a very curious 

 integument, each segment being provided with a 

 ring of cilia-like projections, broad at the base but 

 terminating in a point and soft and flexible in fig. 134.— Mouth-hook 



. , rni • 1 J.1 .• 1 J of the larva of Lesto- 



structure. Ihey are m length sometimes equal to phonus. Greatly en- 

 the widtli of the larva, although usually hardly so '^''S'^*^- (o^sin^i.) 

 long as that. The larva, as seen in the illustration, usually holds itself 

 in the shape of a modified S. Usually there is but one larva to a scale, 

 but at times as many as half a dozen are found. 



