THE iMUNTlllA 151 I.LEThV. 



389 



THE MATURE LARVA. 



The full-fed larva presents a quite ditfereiit appearance from the 

 young form. It is now no longer S-shaped, but is more properly 

 described as pear-shaped. The two tails have become enormously 

 lengthened, sometimes as much as three-fourths of an inch, and this is 

 contained within a host which is frequently not more than 2 mm. in 

 length. The mouth parts have undergone a considerable change, being 

 relatively much shorter and stouter. The larva in this stage begins 

 rapidly to destroy the tissues of the host, the latter now taking on a 

 peculiar convex appearance which renders it easy to recognize the 



^- 



Fig. 135. — The mature larva of Lestophonus. (Original.) 



parasitized individuals at a glance. The tracheal system is conspicu- 

 ous, the anterior branches ending in a pair of horn-like projections 

 which later penetrate the scale of the host and extend to the outside, 

 apparently for the purpose of supplying the parasite with air. On 

 the dorso-posterior part of the larva appears a pair of curious claw- 

 like hooks, which apparently aid the larva in its feeding by giving it 

 a secure base from which to work with its powerful mouth-hooks. The 

 larva now becomes opaque reddish within, due to the tissues of the 

 host which are contained in its intestines. 



THE PUPARIUM. 



The pupa is enclosed within the hardened contracted larval skin 

 which forms the puparium in which the transformation takes place. 



Fig. 136. — Puparia of Lestophonus. Enhirged. (Original.) 



This is soft and yellowish at first, but soon hardens and changes to a 

 reddish brown color. It is long oval, averaging 2 mm. in length and 

 a little more than one-half that in width, tapering about equally at the 

 two ends. Ten segments are readily visible, three of these being 



