264 KEPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



Having described in a very general way tbe digestive canal of tbe 

 locust, we may state in a summary way tbe functions of tbe different 

 divisions of tbe tract, following tbe conclusions of Prof. F. Plateau.*^ 

 Tbe food after being cut up by tbe jaws is acted upon wbile in tbe crop 

 by tbe salivary fluid, wbich is alkaline, and possesses tbe property, as 

 in vertebrates, of rapidly transforming tbe starcby elements of tbe food 

 into soluble and assimilable glucose. Tbe digestive action carried on 

 in tbe crop [ingluvies] tben, in a vegetable- feeding insect like tbe locust, 

 results in tbe conversion of tbe starcby matters into glucose or sugar. 

 Tbis process goes on very slowly. Wben digestion in tbe crop bas ended, 

 tbe matters submitted to an energetic pressure by tbe walls of tbe crop, 

 wbicb make peristaltic contractions, filter gradually tbrougb tbe sbort 

 small gizzard (proventriculus), directed by tbe furrows and cbitinous pro- 

 jections lining it. Tbe apparatus of teetb does not triturate tbe food, 

 wbicb bas been sufficiently comminuted by tbe jaws. Tbis is proved by 

 tbe fact, says Plateau, tbat tbe parcels of food are of tbe same form and 

 size as tbose in tbe crop, before passing tbrougb tbe gizzard. Tbe six 

 large lateral poucbes (cceca) emptying into tbe commencement of tbe 

 stomacb (ventriculus) are true glands, wbicb secrete an alkaline fluid? 

 probably aiding in digestion. In tbe stomacb (ventriculus) tbe portion 

 of tbe food wbicb bas resisted tbe action of tbe crop is submitted to tbe 

 action of a neutral or alkaline liquid, never acid, secreted by special 

 local glands or by tbe lining epitbelium. In tbe ileum and colon active 

 absorption of tbe liquid portion of tbe food takes place, and tbe intes- 

 tine proper (ileum and colon) is tbus tbe seat of tbe secondary digestive 

 pbenomena. Tbe reaction of tbe secretion is neutral or alkaline. Tbe 

 rectum is tbe stercoral reservoir. It may be empty or full of liquids, 

 but never contains any gas. Tbe liquid products secreted by tbe uri- 

 nary tubes are bere accumulated, and in certain circumstances bere 

 deposit tbe calculi or crystals of oxalic, uric, or pbospbatic acid. In- 

 sects, says Plateau, bave no special vessel to carry off tbe cbyle, sucb 

 as tbe lacteals or lympbatics of vertebrates ; tbe products of digestion, 

 viz, salts in solution, peptones, sugar in solution, and emulsionized 

 greasy matters, pass tbrougb tbe fine coatings of tbe digestive canal by 

 osmosis, and mingle outside of tbis canal witb tbe currents of blood 

 wbicb pass along tbe ventral and lateral parts of tbe body. 



Into tbe pyloric end of tbe stomacb empty tbe urinary tubes, tbeir 

 secretions passing into tbe intestine. These are organs exclusively 

 depuratory and urinary, relieving tbe body of tbe waste products. Tbe 

 liquid wbicb tbey secrete contains urea (?), uric acid, and urates in 

 abundance, bippuric acid (?), cbloride of sodium, pbospbates, carbonate 

 of lime, oxalate of lime in quantity, leucine, and coloring matters. 

 - The nervous system. — As observed in Caloptenus spretus, C. femur- 



^3 Eecherches sur les Phenomfenes de la Digestion chez les Insectes. Bruxelles, 1874. 



