1916] Malpighian Vessels of Haltica Bimarginata 397 



into a single tube and a common stem representing a pair of 

 tubes. The single tube, which is very short and delicate, runs 

 quite directly to the mesenteron, where it is inserted isolated into 

 the wall of the intestine, just at the point of junction between 

 the mid-intestine and the hind-intestine. Each common stem 

 soon splits up into two vessels which have a long course through 

 the body cavity. Eventually the four vessels unite to form a 

 single common urinary bladder, which empties into the hind- 

 intestine at a point a little posterior to the insertion of the 

 two shorter tubes. This condition is shown very diagram- 

 matically in Figure 5. 



2. THE GENERAL STRUCTURE OF THE VESSELS OF 

 THE IMAGO. 



The Malpighian vessels of the adult beetle of Haltica 

 bimarginata have exactly the same relations as have just 

 been described for the larva. 



3. A COMPARISON OF THE CONDITIONS IN Haltica bimarginata 



WITH THOSE DESCRIBED FOR CERTAIN OTHER COLEOFTERA. 



Not one of the general features noted above, although very 

 different in many respects from the typical arrangement in 

 insects, is peculiar to Haltica bimarginata, but all of these 

 relations have been described for other forms, although so far 

 as the writer is aware, there has never been a single species of 

 insect recorded in which so many of them were illustrated. 



It has long been known that the Malpighian vessels may 

 have two apparent terminations in the intestine. In all known 

 cases the second termination is merely superficial, in the walls 

 of either the colon or the rectum, and the vessels do not empty 

 into the alimentary canal except at the point of their 

 evagination. 



So far as the writer has been able to ascertain, the earliest 

 work in which there is any reference to such a condition is 

 Ramdohr's paper, which appeared in 1811. He figured the 

 alimentary canals of at least 22 genera of Coleoptera, represent- 

 ing 10 families, 2 genera of Neuroptera, 3 genera of Hemiptera, 

 1 genus of Lepidoptera, and 1 genus of Diptera, in which the 

 Malpighian vessels become reassociated with the alimentary 

 canal at their distal ends, although he did not discuss this 

 point at length. 



