380 NATURAL ARRANGEMENT OF INSECTS. 



they have a small conical head, attached by a tough 

 membrane to the upper anterior surface of the thorax ; 

 two simple eyes placed on each side of its anterior angles; 

 their antennae are two-jointed, flat, and placed closely 

 together within the anterior emargination of the head ; 

 the head, thorax, and abdomen, are distinct ; the legs 

 are long ; tarsi pentamerous, — the basal joint being very 

 lengthy, the terminal joint very robust, and with large 

 claws; and, attached to the base of the intermediate legs, 

 there is, on each side, a curved pectinated process, ap- 

 parently the analogue of Avings. These remarkable insects 

 inhabit different kinds of bats, and, as far as they are yet 

 known, they are peculiar to the Old World, being found 

 in Europe, India, and the Mauritius. 



(342.) Having completed, with the Diptera, the view 

 of six-legged insects that undergo a true metamorphosis, 

 excepting only the small sixth section of the present 

 chapter, containing the Suctoria, we have now to give 

 a summary of the contents of the other divisiops of 

 the Articulata, which have not entered within the pre- 

 ceding synopsis. According to the series above laid 

 down, the ArachnidcB or spiders succeed the Diptera, 

 to which they are apparently allied by the last genus 

 in that order, Nycteribia. Both physiologically and 

 physiognomically, they exhibit marked differences from 

 the true Insecta: thus, the head is no longer distinctly 

 separated from the thorax, and they have no antennse; 

 besides, they have four pairs of legs ; their eyes are 

 always simple, and usually consist of six or eight, dis- 

 posed in a variety of ways on the top of the cephalo- 

 thorax, — the number and arrangement of which have 

 greatly helped towards their systematic distribution. 

 Although possessing no evident and distinct organ of 

 hearing, it cannot be doubted that they have a perception 

 of sound, and touch is acutely performed by their ex- 

 tremely sensible tarsi and palpi. In a large division of 

 them, we observe the usual tracheal respiration of thci 

 hexapod Insecta transferred into a pulmonary apparatus, 

 and in these there is a complete circulating system, which 



