PARASITES THAT ABE FREE WHEN OLD. 177 



The Melophagus of the sheep is a wingless dipterous 

 insect, like the IApoptena of the stag. We give figures 

 of these two curious insects. 



I'ig. 38. — Melophagus ovis. Fig. 39.— Lipoptena of the stag. 



The Stratiome chameleon pays visits to flowers to 

 seek for insects, on whose blood it feeds. Its very elon- 

 gated larva lives in stagnant water. 



We have now to mention in the following passages 

 parasites much less cruel in general, and which receive 

 with greater delicacy the hospitality which is afforded 

 them. We refer to some worms which pass, not their 

 youth, but their mature age in the body of a neighbour, 

 and use their host not as a creche, but as a lying-in 

 hospital. 



Their early youth is passed in freedom, but they 

 soon give birth to a numerous progeny. The fate of the 

 male is unknown ; as to the female, she introduces her- 

 self in a microscopic state into the body of a neighbour, 

 is developed there till she arrives at sexual maturity, 

 and then quits her retreat to go and scatter her eggs. 



It appears, however, that these females are obliged to 

 seek assistance from insects ; but before they enter this 

 living asylum, the male, which is not yet known, ensures 

 by his fecundation the preservation of the species. 



