452 



THE TROPICAL AGRICULTURIST, [December i, 1884. 



different but closely similar plants, infallibly selecting 

 the right food-plant for their larva?. It by no means 

 follows that because we are unable to distinguish two differ- 

 ent plants by their colours, insects cannot : juet as there 

 are sounds inaudible to human ears, so there must be 

 odours imperceptible to human noses: "when," as Mr. 

 Darwin has remarked, " man can perceive no change in 

 plants or animals which have been exposed to a new clim- 

 ate or to different treatment, insects can sometimes per- 

 ceive a marked change. The same species of cactus has 

 been carried to Iudia from Canton, Manilla, Mauritius, and 

 from the hot-houses of Kew, and there is likewise a so- 

 called native kind, formerly introduced from South America, 

 All these plauts are alike in appearance, but the cochineal 

 iusect flourishes only on the native kind, on which it thrives 

 prodigiously." Humbolt remarks that white men " born in 

 the torrid zone walk barefoot with impunity in the same 

 apartment where a European, recently lauded, is exposed to 

 the attacks of the pulex penetrans." This insect, the too 

 well-known Chigoe, must therefore be able to distinguish 

 what the most delicate chemical analysis fails to distin- 

 guish, namely, a difference between the blood or tissues of a 

 European and those of a white man born in the country. 

 But the discernment of the Chigoe is not so surprising as 

 it at first appears ; for, according to Liebig, the blood of 

 men with different complexions, though inhabiting the same 

 country, emit a different odour. "When it is remembered 

 that amougst different but closely allied species of 

 animals some are nauseous to the taste and mal- 

 odorous, while others are the reverse, and the plants 

 that naturally possess a powerful active principle, may, 

 when placed under new and different climatal conditions, 

 wholly lose that active principle, it will not be considered 

 surprising that two species of plants which, like the 

 indigenous and Chinese tea-plants, have been produced 

 under such totally distinct conditions, and diverge from one 

 another in so many important morphological characters, 

 should differ also in chemical quality of their juices. 

 The speculation is most interesting and ingenious, 

 but the question arises, is it correct? Ltt Indian tea 

 planters say. For other reasons than susceptibility 

 to blight, the propagation of China tea in India has 

 long been abandoned in favour of Assam indigenous 

 or hybrids as closely approaching Assam as possible, 

 but, we have never until now seen it stated thai the 

 bug, when it visited a tea district made any such 

 distinction as Mr. Wood-Mason so confidently affirms. 

 If Mr. Peal, who is still living and still adding to 

 the stores of useful knowledge connected with ten, 

 confirms wha', Mr. Wood-Mason states, »e Bball be 

 surprised but saiisfied. At present we strongly doubt, 

 and we regard Mr. Wood-Mason's discovery as to 

 the mode in which the eggs are deposited as the most 

 valuble part of his book. 



The Indian A griculltirist quotes somewhat more largely 

 regarding the " red spider" mite than did the English- 

 man, We copy as follows : — 



The mites lay their eggs in hollows, close to the ribs of the 

 leaves usually. The eggs are oblate spheroids, flatter at one 

 pole, by which they are firmly and broadly attached to 

 the leaves, than, at the other, at which their transparent 

 shell is suddenly drawn out into a long and tapering and 

 slightly curled glassy process. They are red, like the mite 

 itself, aud at the close of sigineutation present at their 

 surface a beautiful reticulated pattern, due to the pre- 

 sence of a concentrated and dark-coloured layer of proto- 

 plsam around the nuclei of all the cells of the blasto- 

 derm. The young arachnids leave the egg as six-footed 

 larva;, which do not attach themselves as parasites to the 

 bodies of insects aud spiders, as do their distant relations 

 the Trombidiida?, nor undergo any of those strange changes 

 ■which many other mites pass through in the course of 

 their development, but attain to the adult condition by a 

 simple change of skin, that usually, though not perhaps 

 invariably, is made on the sameleaf as that on whichthey 

 emerged as. larva? from the egg. The sheils of the hatched 

 eggs, remain glued to the leaf for some time as micro- 

 scopically small objects resembling saucers. 



Preparatory to the final moult the mites draw all their 

 legs in under them, become pertectly motionless, and 



appear to change from red to white ; but no change of 

 colour actually occurs, the appearance of whiteness which 

 the thin and colourless old skin present being due to the 

 access of air to the interval between it and the new. 



The male differs from the female not only in size 

 but also remarkably in the form of the body The 

 former sex is the smaller and in the shape of the body 

 resembles a plover's egg, being broadly rounded at the 

 anterior end and pointed posteriorly while the latter res, 

 embles an egg which is similar an semi-circular in outline 

 and nearly equal at both ends. 



The mode of reproduction is described, and the manner 

 in winch the juices are sucked from the leaves was 

 shown in our extracts from the Englishman. We quote 

 the following description : — 



The tea-mite is an excessively minute animal, the 

 female measuring only about one-twenty-fifth of an inch 

 or about one milimetre in length between the extremities 

 of the outstretched anterior and posterior groups of legs 

 and the male being about one-sixth smaller. The egg 

 shaped body is divided, except when inflated to its fulles 

 extent by imbibed tea-juices, by distinct grooves into six 

 divisions 111 the female and into seven in the male- and 

 each of these divisions, as to which it is exceedingly 

 doubtful whether they represent true segments, bears 

 two pairs of long and stiff and backwardly directed white 

 hairs, forming four longitudinal series placed two on 

 each outer third of the upper surface; the first segment, 

 which has only one pair of hairs, and is moreover, longer 

 in the male than in the female, carries, in both sexes 

 two groups of two unequal eyes, forming two pairs, one 

 of which, the anterior, is smaller than the other. 



To the naked eye the tea-mite appears as a dull 

 blood-red speck, but under the microscope presents itself 

 as a much brighter and more variously coloured object, 

 its legs being of a pale flesh-colour adorned with a light 

 crimson stripe, the front segment of the body bright 

 crimson, with semi-circular mark in the middle of its 

 hinder margin, coucolorous and in contact with the 

 deep blood. red of all the remaining segments in the 

 female (which is dark blood-red from the front en 1 of 

 the second segment to the extremity of the body), but 

 of the four following segments only 'in the male, which 

 has the two terminal segments bright crimson, like the 

 front of the body. The legs are sparingly clothed with long 

 aud colourless hairs, and they are all terminated on each side 

 by pne or two curved bristles, and in the middle by a single 

 hooked claw, on either side of which there spring from 

 the apex of the terminal joint of every limb two delicate 

 glossy threads with enlarged tips forming long and thin 

 stalked suckers, by the aid of which the mites are enabled 

 to retain their footing and walk securely over the leaves 

 and the males to clasp the females firmly by the back 

 dming copulation. In crushed specimens which has been 

 rendered transparent by re-agents, a pair of highly re- 

 fractive and spheroidal solid bodies having a faint concentric 

 structure was always to be made out beneath the skin in 

 front of and internal to the eyes, in a position, therefore 

 corresponding as closely as possible with that in which 

 Claparede never failed to find in embryos, but only in 

 embryos, of T.telarivs, a pair of sacs each containing a 

 pear-shaped solid body. 



I propose for the tea-mite, which would appear to be 

 unknown to science, the name of Tetraaiichus bioculatus, in 

 allusion to its double (really two pairs of) eyes. 

 We cannot help thinking, that, apart from collecting 

 and destroying affected twigs and leaves, as well as 

 the insects themselves and their eggs, the most suc- 

 cessful remedy is likely to be that which has an- 

 swered in the ca '<■ of the phylloxera eggs on vines, viz., 

 a mixture of oil (coconut, or probably better still, 

 castor?), kerosene, quicklime and water. 



As helopeltis generally corfiues itself at first to 

 isolated trees or, small patches in the case of tea, it 

 ought to be pretty easily reached and eradicated. 

 <, 



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