JOURNAIi OF ENTOMOLOGY AND ZOOLOGY 89 



Melasoma [Chrysoiiielal populi. He undertook, however, no 

 detailed study of the internal structure. Lyonet (2) also mentions 

 the existence of these glands. It is also noted by Ratzeberg (3) . 



But the first one to describe the anatomy and histology of these 

 glands was C. Claus (4), who gives an excellent account of those 

 of Melasoma [Lina] populi. Indeed, so detailed and thorough- 

 going is his paper that at first sight it appears almost useless to 

 devote further attention to the subject. There are, however, cer- 

 tain points which were misinterpreted by Claus, and others which 

 escaped his attention. These discrepancies are due to the fact that 

 the modern methods of sectioning were not known at that time, and 

 that the glands were studied /;/ toto, after dissecting them out. Con- 

 sidering the minute size of the glands, the wonder is not that Claus 

 made the few mistakes to be pointed out, but rather that he did 

 not make many more. 



Claus's figures and descriptions have been copied by most later 

 writers, notably by Dimmock ( 5 ) , Packard ( 6 ) , and Schroeder ( 7 ) . 

 Candeze (8) mentions the g\3.nds oi Mel as o?n a \^Chrysomela~\ populi 

 in his paper, saying that the fluid it secretes has the odor of prussic 

 acid. Berlese (9), while citing Claus, gives different figures, which 

 are evidently original. The most notable features of Berlese's 

 figures are the inclusion of a muscle not figured by Claus and the 

 omission of the muscles which Claus does figure, and the figuring 

 of the little chitinized canal in the secretory glandular cells. As 

 will be pointed out later, both Claus and Berlese are correct in the 

 muscles which they figure, but neither has represented the complete 

 arrangement. 



Observations on the Activity of the Glands in the Living 



Larva 



While rearing the larvae of the Melasoma [L/Vm] lapponica, I 

 noticed that when disturbed they ejected a tiny white, pearly 

 droplet from each of the eighteen tubercles already described. 

 The droplets diffused a strong odor, which Professor Riley sug- 

 gested resembled the odor of prussic acid. A test with litmus paper 

 proved the acidity of the secretion. The droplets remained on the 



