. Smithsonian miscellaneous collections. the smallBlattella germanica the bubbles can be seen through the semitrans-parent head wall passing rapidly and in close succession throughthe cibarium. No visible activity of any anatomical parts accompanies no. 7 BITING AND SUCKING INSECTS—SNODGRASS 19 the movement of the bubbles, but it is evident that some suckingmechanism carries them toward the mouth. If the base of the hypo-pharynx is pressed against the inner wall of the clypeus the concavityof the sitophore becomes a closed chamber, and the cibarium couldnow function as a sucking pump by the al
. Smithsonian miscellaneous collections. the smallBlattella germanica the bubbles can be seen through the semitrans-parent head wall passing rapidly and in close succession throughthe cibarium. No visible activity of any anatomical parts accompanies no. 7 BITING AND SUCKING INSECTS—SNODGRASS 19 the movement of the bubbles, but it is evident that some suckingmechanism carries them toward the mouth. If the base of the hypo-pharynx is pressed against the inner wall of the clypeus the concavityof the sitophore becomes a closed chamber, and the cibarium couldnow function as a sucking pump by the alternate action of the dilatorand compressor muscles of its dorsal and ventral walls. Suctionfrom the mouth would seem to be out of the question because there isno postoral pumping mechanism. With the same apparatus the roachimbibes water, but since the flow is continuous there is no visibleevidence of the action of the cibarial pump. To find that the cibariumof a generalized biting-and-chewing insect such as the cockroach may Mai -An. Mth Prvnt Vent AInt Rect Fig. 8.—The alimentary canal of a cockroach, Blattclla germanica (L.),left side. AInt, anterior intestine; An, anus; Cr, crop; GC, gastric caeca; Mai,Malpighian tubules; Mth, mouth; Oe, oesophagus; Phy, pharynx; Prvnt,proventriculus; Rect, rectum; rp, rectal pads; Vent, ventriculus (stomach). function as a sucking organ is most interesting in that it showsthere is no new function involved in the evolution of the suckingpump of the higher insects. THE ALIMENTARY CANAL The alimentary canal begins at the mouth between the upper endsof the suspensory arms of the hypopharynx (fig. 7 A, Mth). As itgoes upward in the head between the two nerve ganglia it widensto form the pharynx (Phy), and then narrows as the oesophagus(Oe), which turns backward over the tentorium and goes throughthe neck foramen to enter the thorax. Here the canal enlarges into abaglike crop, or ingluvies (fig. 8, Cr), that extends into the abdomenand ends
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