212 MANUAL OP ZOOLOGY. 



between them by their apposition. To the base of the trunk 

 are attached the maxillary palpi, which are extremely small. 

 Behind the trunk is a small labium, composed of the united 

 second pair of maxillae. The ' labial palpi ' are greatly deve- 

 loped, and form two hairy cushions, between which the trunk 

 is coiled up, when not in use. 



In the Bee there exists an intermediate condition of parts, 

 the mouth being fitted partly for biting and partly for suction. 

 The labrum and mandibles are well developed, and retain their 

 usual form. The maxillae and the labium are greatly elon- 

 gated ; the former being apposed to the lengthened tongue in 

 such a manner, as to form a tubular trunk, which cannot be 

 rolled up, as in the Butterflies, but is capable of efficient suc- 

 tion. The labial palpi are, also, greatly elongated. 



In the Hemiptera, the ' trophi ' consist of four lancet-shaped 

 needles, which are the modified mandibles and maxillae, enclosed 

 in a tubular sheath, formed by the elongated labium (fig. 62, 3). 

 Lastly, in the Diptera as in the common House-fly there is 

 an elongated labium, which is channelled on its upper surface 

 for the reception of the mandibles and maxillae, these being 

 modified into bristles or lancets. 



The mouth in the Masticating Insects leads by a pharynx 

 and oesophagus into a membranous, usually folded, stomach 

 the 'crop,' or 'ingluvies' from which the food is trans- 

 mitted to a second muscular stomach, called the 'gizzard.' 

 The gizzard is adapted for crushing the food, often having 

 plates or teeth of chitine developed in its walls, and is suc- 

 ceeded by the true digestive cavity, called the ' chylific stomach ' 

 (ventriculus cliylopoieticus) . From this an intestine of variable 

 length proceeds, its terminal portion, or rectum, opening into 

 a dilatation which is common to the ducts of the generative 

 organs, and is termed the ' cloaca.' The oesophagus is usually 

 furnished with salivary glands, and is provided in some of the 

 Suctorial Insects with a dilatation, called the 'sucking sto- 

 mach.' Behind the pyloric aperture of the stomach are a 

 variable number of caecal, convoluted tubes, which open into 

 the intestine, and are called the 'Malpighian tubes.' These 

 are usually looked upon as representing the liver, but are by 

 some believed to have a renal function. If the Malpighian 

 vessels truly perform the functions of a liver as their position 

 would appear to prove then the kidneys will be represented 

 by a series of caecal tubes which open into the rectum, close to 

 the cloaca. There are no absorbent vessels, and the products 

 of digestion simply transude through the walls of the alimen- 

 tary canal into the sinuses, or irregular cavities, which exist 

 between the abdominal organs. The apparatus of digestion 



