132 HUGH GLASGOW. 



able distension. In the adult this anterior division is almost 

 always empty, although in the nymph it is often rilled, and even 

 considerably distended, with a greenish or brownish granular 

 mass, and, as might be expected, it is variable in size and shape 

 in different individuals of the same species. At its posterior end 

 this first stomach narrows suddenly and passes into the com- 

 paratively slender, tubular second stomach which usually is of 

 uniform diameter throughout, and which empties into a second, 

 oval or rounded, dilated portion. This third stomach, in turn, 

 passes abruptly into the fourth and last division, which is the 

 one that concerns us most, as it is on this section of the gut that 

 the caecal appendages with their normal bacteria appear. 



The first stomach is almost always distinct, while the second 

 and third may occasionally grade into each other, in the more 

 specialized forms, in such a way that the exact line separating 

 the two cannot be clearly made out. This fusion is brought 

 about either by the excessive enlargement of the tubular second 

 stomach or by the contraction of. the third, or sometimes by 

 both, and is met with only in those groups in which the caecal 

 appendages are wholly wanting. In those groups in which the 

 csecal appendages are regularly absent, the fourth stomach is uni- 

 formly reduced to an extremely short tubular portion, or it may 

 occasionally be absent altogether, in which case the Malpighian 

 tubes are inserted immediately below the third stomach. 



In certain of the strictly predaceous groups, as in the Reduviidae, 

 Phymatidae, and Acanthiidae, the midgut is very greatly reduced 

 in complexity, there being no trace of the fourth and very little 

 to indicate the second and third divisions, and even the first 

 stomach may sometimes merge into the remainder of the midgut 

 to form an irregular tube of large caliber extending from the 

 oesophagus to the rectum, but without any clear-cut divisions. 

 Even in cases such as this, however, there is usually a slight 

 enlargement at the posterior end, just in front of the point of 

 insertion of the Malpighian tubes; and this may represent the 

 third stomach as it occurs in typical forms. 



The fourth division of the midgut is never well developed except 

 in those families of the Cimicoidea which are provided with 

 caeca, and so far as is known these include only the Pentatomidae, 



