INSECTS AND ARACHNID A. 



235 



( 634), the purpose of which is not apparent; for instead of its tra- 

 cheae being kept pervious, after the usual fashion, by the winding of a 

 continuous spiral fibre through their interior, the fibre is broken into 

 rings, and these rings do not surround the whole tube, but are termi- 

 nated by a set of arches that pass from one to another (Fig. 428, A). 1 

 In the Diptera or two-winged Mies generally, the labrum, maxillae, 

 mandibles, and the internal tongue (where it exists) are converted into- 

 delicate lancet-shaped organs termed setce, which, when closed-together, 

 are received into a hollow on the upper side of the labium (Fig. 428, ), 

 but which are capable of being used to make punctures in the skin 

 of Animals or the epidermis of Plants, whence the juices may be drawn 

 forth by the proboscis. Frequently, however, two or more of these 

 organs may be wanting, so that their 

 number is reduced from six, to four, 

 three, or two. In the Hymenoptera (Bee 

 and Wasp tribe), the labrum and the 

 mandibles (Fig. 429, I) much resemble 

 those of Mandibulate Insects, and are 

 used for corresponding purposes; the 

 maxillae (c) are greatly elongated, and 

 form, when closed, a tubular sheath 

 for the Ligula or 'tongue,' through 

 which the honey is drawn up; the labial 

 (d) also are greatly developed, 



FIG. 429. 



ana fold together, like the maxillae, so 

 as to form an inner sheath for the 

 ' liula ' itself (e) 



' tongue;' while the ** & . 

 is a long tapering muscular organ, 

 marked by an immense number of short 

 annular divisions, and densely covered 

 over its own length with long hairs (B). 

 It is not tubular, as some have stated, 

 but is solid; when actively employed in 

 taking food, it is extended to a great 

 distance beyond the other parts of the 

 mouth; but when at rest it is closely 



packed-lip and Concealed between the prolon^eTlabiumrcommolQiy'terme'd'the 



maxillae. < < The manner," says Mr. New- g^^S^^&S?*" f th * 

 port, "in which the honey is obtained 



when the organ is plunged into it at the bottom of a flower, is by ' lapping,' 

 or a constant succession of short and quick extensions and contractions of 

 the organ, which occasion the fluid to accumulate upon it and to ascend 

 along its upper surface, until it reaches the orifice of the tube formed by 

 the approximation of the maxillae above, and of the labial palpi and this 

 part of the ligula below." 



630. By the plan of conformation just described, we are led to that 



1 According to Dr. Anthony (" Monthly Micros. Journ.," Vol. xi., p. 242), these 

 ' pseudo-tracheae ' are suctorial organs, which can take-in liquid alike at their ex- 

 tremities and through the whole length of the fissure caused by the interruption 

 of the rings; the edges of this fissure being formed by the alternating series of 

 * ear-like appendages,' connected with the terminal ' arches,' the closing-together 

 of which converts the pseudo-trachea into a complete tube. Dr. A. considers 

 each of these ear-like appendages to be a minute sucker, "either for the adhesion 

 of the fleshy tongue, or for the imbibition of fluids, or perhaps for both purposes." 

 The point is well worthy of further investigation. 



