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TEXT-BOOK OF ENTOMOLOGY 



a 



m 



They were first discovered by the Italian anatomist Malpighi, after 

 whom they were called the Malpighiaii tubes. While at first 

 generally regarded as "biliary" tubes, they are now universally 

 considered to be exclusively excretory organs, corresponding to the 

 kidneys of the higher animals. 



Usually arising from the anterior end of the hind-intestine where 

 it passes into the mid-intestine, in certain forms they shift their 



position, in some Hemiptera 

 (Lygaeus, Cimex) opening into 

 the rectum, while in the 

 Psyllidae they arise from the 

 slender hinder part of the mid- 

 intestine, being widely sepa- 

 rated at their origin. (Fig. 

 321.) 



The length varies in differ- 

 ent groups ; where they are 

 few in number (two to four, 

 six to eight), they are very 

 long, but where very numerous 

 they are often short, forming 

 dense tufts, each tuft con- 

 necting with the intestine by 

 a common duct (ureter), or, 

 as in the mole-cricket, the 

 numerous tubes empty into a 

 single duct (Fig. 344) ; in the 

 locusts (Acrydiidse), however, 

 they are arranged in 10 groups, 

 each group consisting of about 

 15 tubes, making about 150 in 



FIG. 344. -Digestive canal and appendages of the a \\ . anc [ are muc h Convoluted 

 mole-cricket : a, head ; ft, salivary glands and recep- 

 tacle ; c, lateral pouch; </, stomato-gastric nerves; an d -\vOUnd irregularly arOUlld 

 e , anterior lobes of stomach ; /, peculiar organ ; y, neck * 

 of stomach ; h, plicate part of same ; i, rectum ; k, the digestive Canal, and when 

 anal gland ; in, urinary tubes. After Dufour, from . 



sharp. stretched out being about as 



long as the entire body. 



The urinary tubes occur in twos, or in multiples of two, though a 

 remarkable exception is presented in the dipterous genera Culex and 

 Psy diodes, in which there are five tubes ; the young and fully 

 grown larvae, as well as the pupa and imago of Culex, having this 

 number (Fig. 433, mg.*) 



