THE ALIMENTARY CANAL OF THE LARVA OF 

 ALTICA BIMARGINATA SAY (Coleopteraj. * 



By William Cor.t ord Woods. 



1. The gross anatomy. 



2. The histological structure of the alimentary canal. 



3. The Malpighian vessels. 



4. The salivary glands. 



1. THE GROSS ANATOMY OF THE LARVAL CANAL. 



In the alimentary canal of the alder flea-beetle, Altica 

 bimargi}iata Say, (Chrysomelidse) as in insects generally, three 

 primary divisions of the digestive tract are at once evident; 

 the fore-intestine (stomodaeum), the mid-intestine (mesenteron 

 or ventriculus), and the hind-intestine (proctodaeum). In this 

 larva, the comparatively short alimentary canal, which is a 

 nearly straight tube with few convolutions, is somewhat less 

 than half again as long as the body. The writer has already 

 published a figure showing the general structure (Woods 

 1916. Fig. 1). 



The alder flea-beetle is entirely a plant feeder, living usually 

 on the leaves of the alder {Alnus iiicana Moench), or more 

 rarel}' on the willow (Salix spp.), or the balsam poplar {Popiilus 

 balsamifera L.). Among adult insects the carnivorous species 

 as a rule have rather short, straight intestines, whereas the 

 phytophagous species tend to have longer and more convoluted 

 digestive tracts. The larva of the alder flea-beetle does not 

 really form an exception to this generalization, although at first 

 sight it may appear to; for the alimentary canal, though short, 

 is of considerable diameter throughout, so that what it may 

 lack in length is made up in volume. Gastric coeca such as 

 are developed in the Acridiidas or in Corydalis are entirely 

 wanting. 



The fore-intestine is short, extending back only as far as the 

 beginning of the second thoracic segment. Two divisions only 

 are recognizable in it upon dissection, but histologically four 

 regions can be distinguished, the first three appearing to con- 

 stitute a single region macroscopically. These parts are first 



Coniriliution from the Entomological Laboratory of Cornell Uni\'ersity. 



283 



