54 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



organ to suck the liquid food of tlie animal througli the proboscis, and 

 force it backwards into the digestive canal, the process being as fol- 

 lows : The proboscis is unrolled, and inserted into the nectary of a 

 flower; at this momeut the muscles which suspend the pharynx con- 

 tract, and its cavity is thus extended, creating a vacuum, which must 

 be supplied by a flow of honey through the proboscis, into the 

 pharynx. When the latter is full its muscles contract, the valve closes 

 the aperture to the proboscis, and the honey is forced backward into 

 the oesophagus. The pharynx is then again opened, and the same pro- 

 cess is repeated. To prevent the food being sucked back from the 

 oesophagus, it is probable that some of the numerous fibers in the 

 muscular sac near the origin of the former can, by contraction, close 

 its opening; but in any case, as the proboscis presents a free tube, and the 

 oesophagus leads into the closed alimentary canal, it is evident that the 

 former offers the easiest route for a supply to fill the vacuum produced 

 in the pharynx." (Burgess.) 



The organ just described escaped the notice of entomotomists until 

 discovered by Burgess, and its functions were coujecturally ascribed to 

 other parts. " The so-called ' sucking stomach ' thus received its name 

 from earlier writers, and when its structure was better known and such 

 a purpose negatived, the capillarity of the fine tube of the proboscis, 

 and even a peristaltic action of the latter, have been suggested to ex- 

 plain the power possessed by the butterfly to suck up its food." 



At the upper extremity of the pkarynx oi)ens the narrow oesophagus, 

 oe, and at the lower edge of the hypopharynx the common duct of the 

 salivary glands, sal, discharges into the expanded base of the probos- 

 cidean canal. These glands consist of two long convoluted tubes, ex- 

 tending along each side of the thoracic central nervous system. In 

 the general figure, Plate YIII, Fig. 2, the glands have been removed, 

 in order to show the course of the oesophagus and ganglionic chain. 



The oesophagus, Plate YIII, Pig. 2, oe, is a slender and delicate tube 

 leading from the pharynx above, and after x)ierciug the nerve commis- 

 sure between the brain and the succeeding ganglion, passes straight 

 through the thorax into the abdomen, in the very base of which it 

 separates into two short branches, the upper leading into the food res- 

 ervoir, the other the true stomach. 



The food reservoir, fr, (or so-called sucking stomach), is a large 

 membranous sac filling the anterior end of the abdomen; its walls are 

 a very delicate cuticle, which is interiorly thrown into very curious laby- 

 rinthine wrinkles; near the neck is a region armed with singular processes 

 or spines, scale-like in shape, each scale being armed with some six or 

 eight very sharp teeth. The neck has an investment of transverse, an- 

 nular muscular fibers. 



In alcoholic specimens the food reservoir is much crumpled, and in 

 all specimens opened was empty. There are some indications that the 

 sac is not a simple one, but has secondary lobes or partitions ; but this 



