352 PHYSIOLOGY. 



mouth or pharynx likewise lies at the base of this proboscis covered by 

 a valve, as in the wasps. From it the simple proboscis passes on to the 

 stomach, distending in front of the latter into the sucking bladder. A 

 peculiar vessel originates from the canal of the proboscis, the course of 

 which indeed Treviranus could not completely follow, but which pro- 

 bably passes beneath the cerebellum and opens into the oesophagus ; 

 the ducts of the salivary glands also appear to open into the oesophagus. 

 Treviranus therefore considers that this canal within the proboscis is 

 the organ which imbibes the nectar, but he passes over in silence the 

 function of the mouth, or orifice of the pharynx. If, however, I shall 

 not undertake to question the justice of his remarks without adequate 

 investigation, it yet strikes me as evident that the oral aperture or 

 orifice of the pharynx must have some particular and important relation 

 to the mechanism of nutrition, perhaps harder and larger particles of 

 food, such as the grains of pollen, are swallowed by it, or, which is yet 

 more probable, that the honey, which the neuter bees are known to cast 

 up, is rejected through this aperture. 



The suctorial apparatus of the Lepidoplera differs still more widely. 

 Their oral organs consist of two spirally convoluted hollow probosces, 

 which represent the maxillae of other insects (see the detailed descrip- 

 tion of these organs at 70). Into each of these sucking tubes a 

 branch of the furcate oesophagus opens ( 102). This itself is a nar- 

 row tube, which becomes the stomach at the commencement of the 

 abdomen ; and here, closely in front of this transition, it has a simple or 

 double sucking bladder. The two probosces form, united, a central canal, 

 into which the ducts of the salivary glands open. In these insects 

 therefore the simple oral orifice has entirely disappeared, instead of 

 which we find two proboscideal sucking mouths, through which the 

 nectar, which is the universal food of the Lepidoptern, ascends, by the aid 

 of the sucking bladder, and by means of the above described mechanism. 

 Another corroboration of the correctly supposed function of the bladder, 

 and of its connexion with the business of sucking the aliment, is found 

 in its being very small in those Lepidoptera which have a short conical 

 proboscis, as in Euprepia caja and Cossus ligniperda, whereas in the 

 butterflies, which have a long proboscis, and also in the sphinges, it is 

 of large compass. 



The proboscis of the Diplera has been already above ( 70) amply 

 described ; and we have also learnt from the anatomical description of 

 the intestinal canal ( 103) that they have a large sucking bladder, 



