394 Annals Entomological Society of America [Vol IX, 



two vessels leave the intestine side by side, and very close 

 together, but are entirely independent of one another. It 

 should not be inferred from any of the above statements that 

 the writer regards the second series of tubes as appendages 

 of the mid-intestine. The epithelium of that portion of the 

 ileum into which both series of vessels empty is strikingly 

 different from that of the remainder of this division of the 

 intestine, and the cells of the Malpighian vessels are very 

 different from those of the mid-intestine. The second series 

 of vessels, as well as the first, belongs to the hind-intestine. 



The two vessels which constitute the second series are very 

 much shorter than the four tubes of the first series. They extend 

 only a short distance anteriorly, usually following the twisting 

 of the mesenteron, and then run more or less directly to the 

 junction of the ileum and colon. Under the binocular these 

 vessels appear more delicate than those of the first series, the 

 diameter is slightly less, the cells are slightly smaller, and in 

 color they are more or less a translucent white, instead of 

 being opaque. 



Thus far we have traced the course of the four vessels of the 

 first series and the two vessels of the second series, and have 

 seen that all six finally extend to the vicinity of the strong 

 bend caudad in the alimentary canal, which marks externally 

 the end of the ileum and the beginning of the colon. 



The four vessels of the first series, which represent two 

 pairs, at the distal ends of their coelomic portions unite into 

 two common stems, consisting of two vessels each. One of the 

 short vessels of the second series soon becomes closely associated 

 with each stem, and thus all six of the tubes have now been 

 accounted for. Each stem with its apposed vessel applies 

 itself closely to the wall of the colon, one on the dorsal side and 

 one on the ventral. Up to this point the vessels of the second 

 series remain distinct, but here each fuses with the stem with 

 which it is associated, and thus two common trunks, represent- 

 ing three vessels each, are formed, one lying on the dorsal 

 wall of the colon and one on the ventral wall. 



In Haltica bimarginata the colon consists of the following 

 parts, passing toward the exterior: intima, epithelium, base- 

 ment membrane, circular muscle layer, longitudinal muscle 

 layer, (and later a layer of Malpighian vessels and a peritoneal 



