50 



HARDWICKE'S SCIENCE-GOSSIP. 



[March 1, 1868. 



of which the first and second are short and stout, 

 the third by far the longest, while the last is thin, 

 transparent, retractile, and furnished with four 

 claws. There is no "pulvillus" or sucker situated 

 between the claws, as in most of the Acari ; for the 

 very sufficient reason that such an instrument is 

 scarcely needed by a creature which, in its natural 

 condition, seldom if ever places its foot on a smooth 

 polished surface. Living as they do on a web composed 

 of innumerable threads, they are furnished with a 

 far more efficient and useful apparatus in the four 

 claws (an unusually large number) and a tuft of 

 stiff hairs which lies at their base, and which, I 

 have little doubt, is intended to aid them in cleansing 

 and disentangling the threads ; answering in this 

 respect to the comb-like processes with which so 

 many of the spiders are provided. 



The claws themselves are exceedingly elastic, the 

 horny substance of which they are composed being 

 seen to give way before the pressure of the covering- 

 glass, again recovering itself when the pressure 

 is removed. They are also very flexible, bending 

 inwards like the fingers of a human hand, when the 

 last joint of the leg is retracted. Doubtless, this 

 provision enables the tiny animals to lay firm hold 

 of the threads of their web, and to grasp them 

 tightly when running across it, or when shaken by 

 the wind or a blow. The web is an interesting 

 object, of a blueish colour when complete, and made 

 up of innumerable separate threads of a uniform 

 texture and appearance. I have never been able to 

 detect exactly the manner in which the web is 

 formed, as the spinning apparatus is situated on the 

 lower surface of the abdomen, and the movements 

 of the animal are far less sluggish and dull than in 

 many of their fellow-Trombidians. All the observer 

 can see is a continuous thread, which seems to have 

 no limit, issuing from below the little creature, and 

 following its movements in every direction. I 

 should imagine that the spinneret is situated at 

 about the third quarter of the abdomen, counting 

 from the head, because when the animal is disturbed 

 in its onward path, and turns suddenly to the- right 

 or left, the thread may be seen coming out from 

 between the two posterior legs. It is curious to 

 watch the tiny spinner in such a dilemma, raising its 

 legs and stepping over the obstacle formed by the 

 thread with the utmost sangfroid. The thread has 

 no little strength and tenacity, for I have seen it 

 pressed with considerable violence, and without 

 breaking, against one of the hind legs, when the 

 animal draws it " taut " in turning. The web is 

 formed very quickly by the incessant action of 

 hundreds of minute workers, apparently moving 

 without fixed order or special object, crossing and 

 rccrossing each other at every possible angle, but 

 in the end producing a network of tent-like form, 

 bluer aud thicker at the top than at the bottom. 

 There are no glutinous threads at stated intervals, 



as in the webs of the true Arachnids, though the 

 threads themselves are to a certain extent viscid 

 throughout. I base this statement on the fact that 

 when the little animal, in the act of traversing the 

 stage plate of the microscope, twdsts itself about 

 and moves in another direction, the thread invari- 

 ably clings to the point where the turn occurred, and 

 remains adhering to the glass, though of course no 

 little stress is laid on it, as it tightens under the 

 animal's onward progress. 



In this transparent cone, which is w T oven at the 

 apex of a twig of furze, the little family remains en- 

 closed, in active movement during the day, but each 

 night retiring under the shelter of the gigantic tent- 

 pole or column, which forms the centre of their 

 home. Gradually, however, they extend themselves 

 on each side, and although, as far as my observa- 

 tions extend, they never voluntarily leave their 

 " cocoon," no doubt numbers of adventurous 

 youngsters who are eager to see the world from the 

 outside of their silken canopy, get blown away 

 during high winds and violent storms, and thus 

 extend the bounds of their habitation very much 

 against their own will. 



In spite, however, of their great fecundity, and 

 their probable dispersion by means of the wind,, 

 these mites seem to be anything but common. We 

 have seen that in 1855 they were unknown to 

 Dr. Barry, and to " the Araclmologist," Mr. Meade; 

 nor am I in a position to add any more information 

 than what has been forwarded to me by Mr. White, 

 of Budleigh Salterton, Devonshire, who says : " I 

 have noticed them on our gorse bushes from time 

 to time for many years. 1 cannot say whether they 

 are to be found all the year, but I distinctly remem- 

 ber seeing some in December, January, February, 

 and March. In the latter part of June I could not 

 find one ; and though I searched diligently, it was, 

 I think, the end of August before I discovered any 

 more, and these were in a locality in w'hich I had 

 not previously noticed any. I now know of only 

 two or three bushes on which there are any." 



I suspect the fact to be, that partly from their 

 minuteness and partly from their web being so like 

 that of some spider, they are constantly overlooked. 

 But perhaps some of the correspondents of Science- 

 Gossip may enlighten us on this point. I have 

 succeeded in establishing a colony on a furze bush 

 in this neighbourhood ; greatly, by the way, to the 

 amusement of my unscientific acquaintances ! When 

 last seen, about a fortnight ago, they had attached 

 themselves to their new home, and were safely con- 

 cealed under their cauopy of silk, in spite of a good 

 deal of rough weather; and I hope I may be able to 

 report their well-doing in the spring. 



Of the numerous species belonging to the present 

 family of Trombidida?, described by continental 

 acarologists, I know of but two that come at all 

 near, either in structure or appearance, to the one 



