12 



INTRODUCTION . 



elongate so that it is coiled and like an intestine in shape ; in the 

 Coleoptera it often bears elongate diverticula or pouches, especially 

 on the anterior part, these being sometimes (e. g., Carabus) so 

 numerous that the whole surface seems villose, In some cases this 

 stomach seems to be divided and the hinder part appears to be a 

 portion of the small intestine ; but the point can easily be settled 

 by the position of the Malpighian tubes, which are always attached 

 at the junction of the stomach and intestine. This mid-intestine 

 varies very much in the Coleoptera. In the Lamellicornia (Melo- 

 loniha and Geotrupes) it is very long; in Meloe exceedingly large, 

 occupying most of the body-cavity ; while in the Longicornia it is 

 very small. 



The small intestine, or, as it is usually called by those who re- 

 gard the mid-intestine as the true stomach, " the intestine," is also 

 very variable. The anterior part, which is slender, is called some- 

 times the small intestine, or the ileum ; in some of the Adephaga, 

 as Dijtisms, and in Necrophorus it is very long, but it is rather 

 slender and short in the Carabine and Cicindelice, as well as in 

 those insects whose food is liquid, such as Diptera. In the 

 Lepidoptera it varies in length, being in Sphinx quite long and 

 bent into seven folds, while it is short in the Cheysomelidje, and 

 also in the Psocid^; and Tenthredimid^e. The part next to the 

 ileum is called the colon, while the terminal section forms the 

 rectum ; the colon, however, is sometimes regarded as merged in 

 the rectum. In butterflies and probably in most Lepidoptera, the 

 colon is distinct and is anteriorly developed into a large bladder- 

 like caecum. In certain Coleoptera (e. g., Di/tiscus, Silpha, and 

 Necropliorus) this caecum is of remarkable length and shape. The 

 rectum, when separate, is larger than the colon, and is furnished 

 in many insects with peculiar structures called rectal glands ; these 

 are very conspicuous in certain Orthoptera, and are found among 

 the Coleoptera ; whether they are really glands is very doubtful, 

 from their structure and position. Fernald regards the rectal 

 glands of Passalus as " acting like a valve, serving to retain the 

 food in the absorptive portions of the digestive tract till all 

 nutriment is extracted" (Packard). 



The anus is situated at the end of the body and is present in all 

 the Coleoptera both in the larval and perfect state. Connected 

 with the anus are certain " eversible repugnatorial glands," called 

 ordinarily the anal glands, of which a long and interesting account 

 is given by Packard (Text-Book of Entomology, pp. 372-380). 

 These glands secrete pungent and corrosive fluids which can be 

 ejected sometimes to a considerable distance, and form a very 

 effective means of defence ; they are especially noticeable in 

 certain Californian species of Eleodes, which Williston describes 

 as the " veritable skunks of the order," and also in Blaps. 



''* Similar glands, though usually smaller, which have not been 

 carefully examined, occur in Carabus and Cyclirus, which eject 

 from the A^ent a disagreeable fluid containing butyric acid. The 



