IOOS INSECTS AND ARACHNIDA 



it has been confirmed by the subsequent investigations of Mi-. 

 Lowne. 1 



The Arachnida, or scorpions and pseudo-scorpions, and the J/-<Y- 

 neida or spiders, present much that is of interest even to the unscien- 

 tific who use the microscope only for pleasure. The general remarks 

 which have been made in regard to insects are equally applicable 

 to these, but have special application in that group known as the 

 Acarina, consisting of the mites and ticks. Some of these are 

 parasitic, and are popularly associated with the wingless parasitic 

 insects, to which they bear a strong general resemblance, save in 

 1 laving eight legs instead of six. The A<:i-imt are the true ' mites ; ' 

 they generally have the legs adapted for walking, and some of them 

 are of active habits. The common cheese-mite, as seen by the naked 

 eye, is familial' to every one ; yet few who have not seen it under a 

 microscope have any idea of its real conformation and movements ; 

 and a cluster of them, cut out of the cheese they infest, and placed 

 under a magnifying power sufficiently low to enable a large number 

 to be seen at once, is one of the most amusing objects that can be 

 shown to the young. There are many other species, which closely re- 

 semble the cheese-mite in structure and habits, but which feed upon 

 different substances ; and some of these are extremely destructive. 



The Aciirina are the smallest of the .1 rllir<>i>,l.(i, and are specially 

 well fitted for microscopical examination ; indeed, with the exception 

 of the Ixodidce (including the Aryos'um'), which attain a substantial 

 si/.e, particularly in tropical countries, but little can be learnt 

 respecting them without such aid; as far as is at present known. 

 other mites are not larger in hot countries than in Europe. 3Lmv 

 species make beautiful objects for the microscope, and may be well 

 preserved, the hard-bodied specimens in balsam without heat or 

 pressure, the soft-bodied in glycerin or glycerin jelly : e.g. the 

 nymphs of Leiosoma palmacinctu/m, Tegeocranas cepheiformis, T. 

 dentatus, and the adults of (Uyciplmgns plwnig&r and <!. jn/lniifi-/- 

 are admirable. They are all British, and are found respectively on 

 lichen at the Land's End, on the fallen bark and needles of fir-tree-. 

 on fallen oak-wood, in the fodder in stables, and on cellar-walls. 

 Many of the T>i>mhiiHi<l<> and HydrachnidcK also are very beautiful : 

 and the Dermaleichi. especially the males, and such creatures as 

 M i/f>l>i<t, Listrophorus, AT., are extremely curious. With the excep- 

 tion of the Phytoptidce, all Ai-nr'mti in the adult stage have eight 

 legs and the constriction between cephalo-thorax and abdomen. is 

 Car less marked than in insects and spiders in manv genera it is 

 wholly lost. The sexe> are distinct and often very different from 

 each other; the reproduction is oviparous or ovo-viviparous pos- 

 sibly in rare and exceptional instances viviparous. The ova are 

 usuallv elliptical or oval : in those which have a hard shell a 

 curious stage known as the deiitov ium exists; as the egg increases 

 in si/.e the shell splits into two symmetrical halves, which remain 

 attached to the lining membrane, but are widely separated, the 



]{< 'I'm 'in ! slmiild tic ni.nlr in Professor liiitschli's observations in Morpliol. 

 li, xiv. p. 17<i, JIM |L-. Viirlt/liiiw's ]I.I|HT in Arbeit. Zool. Ziinl. lust. Wilrz- 

 ix. p. 1. 



