J. J. WRIGHT ON THE HARVEST BUG. 3 



have been supposed to pass, such as the red line, or burrow of the 

 itch insect when it leaves its pustule. They may sometimes be 

 observed adhering to the skin at the top, and centre of the wheals, 

 after these are fully formed ; at a period therefore, when, if they 

 burrowed, they might be supposed to be concealed from view. 

 When examined on the skin, the head, or part of the head is some- 

 times seen partially covered with an epithelial scale; and this is the 

 nearest approach to burrowing which I have ever noticed. When ob- 

 served upon the skin it gives the impression that the lancets are buried 

 in its substance, while the mandibles and claws firmly grasp the hairs, 

 or inequalities on the surface of the skin. They are extremely 

 difficult to remove without completely crushing them, so tena- 

 ciously do they adhere. No central puncture can be detected in the 

 wheal, as in the case of the bite of a bug, flea, or gnat : and this 

 may perhaps be urged as a reason for supposing that the lancets 

 of the Harvest Bug do not pierce the skin. But its lancets are ex- 

 tremely small as compared with those of the insects just mentioned, 

 and they are so arranged as to make an essentially different kind 

 of opening. Penetrating the skin directly downwards, and then 

 diverging in the same plane, they will make something like a 

 simple incision, which from its form, and extreme minuteness, and 

 from its tendency to close accurately the moment the lancets are 

 withdrawn, would be far more difficult to detect than the large and 

 circular puncture of the flea. Further, if the wheal from the sting 

 of a nettle be examined, which is extremely like that produced by 

 the bite of the Harvest Bug, it is impossible to detect the point 

 at which the sting has penetrated, though we are quite sure there 

 has been a penetration, and the injection of an acrid fluid. Again, 

 it may be objected, if the incision be so minute and simple in its 

 form, why should it excite irritation so severe? I suspect, though 

 this is certainly only a conjecture, that an irritant fluid is poured 

 into the wound through the minute line, or tube, which passes 

 through the centre of the lancets. This line appears to me to 

 bear a strong analogy to the hollow tube which passes through the 

 fangs of the spider, and which we know to be connected with a 

 poison sac. That an acrid fluid is injected is also rendered the 

 more probable from the striking resemblance between the effect pro- 

 duced by the sting of the nettle, and the bite of the Harvest Bug. 

 Suppose the insect does burrow beneath, or embed itself in the skin, 

 what is the object to be accomplished ? It neither deposits its 



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