THE STRUCTURE AND METAMORPHOSIS OF THE 



ALIMENTARY CANAL OF THE LARVA OF 



PSYCHODA ALTERNATA SAY.* 



By Leonard Haseman. 



The changes which take place in the digestive epitheHum 

 of insects after feeding, and in connection with the molting 

 periods, have been but little studied, though in the cases 

 known the phenomena are of great interest. In some insects 

 partial, in others, total regeneration of the mid-intestinal epi- 

 thelium has been found to occur after each taking of food. 

 In other instances it is the changes associated with molting 

 which have attracted attention. It was with a' view of study- 

 ing the morphological changes in the epithelium at the two 

 periods and of correlating the results with those of previous 

 workers that this study of the larva of Psychoda alternata 

 was undertaken. 



A review of the literature shows that but little has been done 

 along these lines with larval forms. Aside from the work of 

 Van Gehuchten ('90 and '93) on Ptychoptera contaminata, 

 Moblisz ('97) on Anthrenus and Folsom and Wells ('06) on 

 Collembola, we find only scattered references here and there 

 in more general papers on the digestive system. Psychoda 

 alternata has been selected for the present work because of the 

 ease with which it can be secured and bred throughout the year, 

 its wide distribution, its convenient size for work and the fact 

 that it is one of the most generalized Diptera. 



This study was carried out in the Entomological Labora- 

 tories of Cornell University, and to Professor J. H. Comstock, 

 I am greatly indebted for valuable suggestions and criticisms. 

 The subject was suggested and the work done under the imme- 

 diate supervision of Dr. W. A. Riley, to whom I am especially 

 obligated for constant advice and help. 



THE STRUCTURE OF THE ALIMENTARY CANAL. 



The alimentary canal of the larva of Psychoda alternata 

 is a straight tube extending from the mouth to the anus, with- 

 out folds, except during bodily contraction when a slight one 

 is formed in the region of the small intestine. Aside from the 

 attachment of strong pharyngeal muscles and the Malpighian 



'^Contribution from the Entomological Laboratories of Cornell University. 



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