ENEMIES OF APHIDES. 41 



longitudinal muscular fibres respectively, giving it exteriorly a 

 rugged aspect, and the membranous coat bears on its interior 

 surface a lining of epithelial cells. The passage towards the crop 

 or sucking stomach is shown at k, and here the circular fibres have 

 become few, while the longitudinal and membranous coats are 

 developed, until the crop itself is reached, when the muscular 

 bands interlace in all directions, especially about the centre. The 

 organ shown in the figure is collapsed or empty, but when occupied 

 with food it presents the appearance of a seamless, distended bag, 

 around the middle of which a broad constricting band divides it 

 into similar hemispherical parts. Its surface when distended is 

 smooth and free from corrugations, but displays the numerous 

 crossing bands of muscular fibre, by means of which the food is 

 regurgitated, to find its way to the proventriculus, m, and the 

 " chyle stomach," or digestive stomach, /. The proventriculus is 

 embraced by the upper portions of a pair of sacculated glands, 

 «, n, which secrete some gastric or other fluid, to assist in the 

 digestive operation. 



The digestive stomach, /, which presents no points of special 

 interest, opens by a muscular neck more or less developed into 

 the upper intestine, p, which in the figure is distended by food, 

 and which at its lower end receives the secretions of the four 

 elongated hepatic glands, g., g. These glands are objects of great 

 beauty. The arrangement of the nucleated cells on either side of 

 the tube, which constitutes their main structure, gives them the 

 appearance of a regularly knotted rope, and frequently the whole 

 organs are of a brown or beautiful purple colour. 



At the extremity of the intestine. a powerful muscular valve 

 controls the passage of food to the lower intestine, r. This 

 intestine is much stouter in its structure, the rugose outer surface 

 presenting at times an almost sacculated appearance, and at its 

 lower end it passes into the rectum by an internal muscular con- 

 traction not readily observed, as the external wall is often not 

 contracted. The rectum (v, v) is noticeable for the great 

 development of the renal organs (^, t), which are found, four in 

 number, in an ovoid enlargement at s. These organs are of great 

 interest, and may readily be obtained from a recently killed 

 insect. They will be fully described and illustrated in the next 



