CHAPTER III. 



THE INTERNAL STRUCTURE OF ANTS. 



" In his tarn parvis, atque tain nnllis, qua; ratio, quanta vis, quse inextricabilis 

 perfectio !" Pliny, " Historia Animalium," NT, 2. 



The Alimentary Tract. This extends the entire length of the body 

 from the mouth to the anus as a tube with but a slight tendency to 

 convolution in the gaster. The walls of this tube are curiously modified 

 in different portions of its length, so that we can recognize a number of 

 regions known as the infrabuccal chamber, buccal tube, pharynx, oesoph- 

 agus, crop, proventriculus, stomach, small intestine and rectum. The 

 shape and extent of these regions are indicated in the accompanying- 

 diagram taken from Janet ( Fig. 13 ). Owing to the volume of the brain 

 and cephalic glands, to the narrowness of the thorax and pedicel in the 

 worker, and the great development of the wing muscles and glands in 



X 



FIG. 13. Sagittal section of worker Myrmica ritbra. (Janet.) t, Tongue ; Ibr. 

 labrum ; dp, clypeus ; sg, opening of salivary gland; bo, mouth opening; lip, infra- 

 buccal chamber; ph, pharynx; phg, pharyngeal glands; oe, oesophagus; cr, crop; gz, 

 gizzard ; st, stomach ; lin, large intestine ; nip, Malpighian vessels ; re, rectum ; rcg. 

 rectal gland; an, anus; fgl, frontal ganglion; rcc, recurrent nerve: br, brain; mdg, 

 mandibular ganglion ; m.rg, maxillary ganglion ; Ig, labial ganglion ; soc, subcesophageal 

 ganglion ; cho, prothoracic chordotonal organ ; thg', tlig-, tlig 3 , pro-meso- and meta- 

 thoracic ganglia; ag'-ag 2 , ag, 8-u, first to eleventh abdominal ganglia; sym, sympa- 

 thetic connective, running along oesophagus to prestomachal ganglion ( stg) ; st, sting ; 

 i'g, vagina ; ten, tentorium in section. 



the thorax of the male and female, the alimentary canal is cramped for 

 space and hence very tenuous, except in the gaster, where its most 

 important parts are situated. The mouth opening, which, as we have 



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