228 



HARDWICKE'S SCIENCE-GOSSIP. 



its colour to that of the plant or animal on which it is 

 feeding. We have found it of a reddish-straw colour 

 in the hai-vest-field, quite green on green plants, and 

 perfectly crimson on — or more correctly in the skin of 

 — the human body. We have also placed the insect, 

 when green, on the back of the hand, and watched 

 its mode of attack and change of colour. 



On being placed in a green state on the hand, 

 it commences to use its pointed, spear-like mandibles 

 (yJ/ in fig. 174) vigorously, and a sense of pain 

 is quickly experienced. In two or three minutes 

 it begins to imbibe the human blood, still vigorously 

 working with its mandibles, and forcing its way 



state of the blood. Once embedded in the skin, the 

 han'est-bug appears to have no power of extricating 

 itself, A state of torpidity soon sets in, peihaps at 

 once, and after a few hours the little creature ceases 

 to exist. The irritation may continue, however, in a 

 sensitive person for two or three days. 



The question now arises : — To what is the irritation 

 due ? To the mere puncture it can scarcely be. Is 

 it, then, to a poisonous fluid injected, or is it to the 

 numberless cilia-like spines or stilettos with which the 

 body and legs of the insect are covered ? We have 

 not yet satisfied ourselves on this point, but are 

 inclined to think that it is due to the latter. The 



Fig. 174. The Harvest-hug (,Le/ius nuiuiuriaiis), highly magnified. 



under the skin. After the lapse of two or three more 

 minutes it may be seen, by the aid of an ordinary 

 pocket lens, to have sensibly changed colour, and 

 in from fifteen to twenty minutes from the first, it will 

 be seen to be quite crimson, and so thoroughly em- 

 bedded in the skin that nothing short of a slight 

 surgical operation, which may be performed with a 

 sharp-pointed needle, will remove it. During this 

 time a slight pain is experienced, but it is after the 

 little creature is fairly embedded in the skin that the 

 irritation is most painful, and the swelling commences. 

 In many cases the swelling thus raised is two or three 

 hundred times the size of the insect. By numbers of 

 people these swellings are called /leat hinnps, and 

 were believed to result from a heated or disordered 



prolonged irritation may be in part, or altogether, due 

 to the decomposing body of the insect in the skin ; a 

 poisonous fluid being thus generated. This hy- 

 pothesis is borne out by the fact that the irritation of 

 the punctures from which the insects have been 

 removed ceases much sooner than that of those in 

 which the insects are allowed to remain. At the 

 same time it must be remembered that this may be 

 due to the absence of the mechanical irritative body. 



Another interesting question also arises : — Does the 

 blood extracted from the human body by the insect, 

 which imparts to it its crimson colour, undergo any 

 change in the system of the insect? We believe it 

 does, but only a mechanical change, the human 

 blood corpuscles being broken up sufficiently fine to 



