70 



The Larva of Chironomiis 



colon ; they Lave also been found in young embryos of 

 Hydrophilus ^ and in plants (endosperm of Fritillaria, 

 &c.). The physiological meaning of the structures has 

 not been elucidated. 



The salivary fluid is used in the form of silken threads 

 to weave together the vegetable or earthy particles of 

 which the wall of the burrow is composed. We have no 

 reason to attribute to it any digestive property, and its 

 rapid coagulation on contact with water renders it hard 

 to suppose that it can act upon food which is necessaril}'- 

 mixed with water. 



The salivary ducts pass off from the inner or concave 



sides of the glands. They 

 have a ringed (' pseudo- 

 tracheal ') structure, like 

 that of insect air-tubes. 

 They pass forwards to the 

 tubule ofT^fvf^''^"'^ """' "*' *^'^'i''^^"^'" head, and enter the iloor 



of the mouth beneath the 

 lingua (fig. 19, sd). The common duct is extremely short. 



Ganin '^ and Bugnion •'' find that in Hymenoptera the 

 salivary glands are developed independently of the 

 alimentary canal from a special ectodermal invagination. 

 Carriere (1897), adopting the earlier suggestions of 

 Biitschli and Grassi, derives them from the prothoracic 

 spiracles, which, he says, in Hymenoptera open at first 

 inside the second maxillae, and become approximated 

 and at length fused as the maxillae unite to form the 

 labium. 



Maipighian There are four long Alalpiyhian tubules, which enter 

 the dilated beginning of the small intestine. They are 

 lined by an epithelium of flatfish cells with large 



^ Carnoy. 1885. 



^ ' Ueb. d. Embiyoiialhiitte dtu- Ilymenoptereu u. Lepidopteren- 

 Embryonen.' Petersb. Acad. Sti., xiv (i87o\ 



' *Anat. et moeui-i de I'Encyrtus fuscicollis.' Fee. Zool. Suisse, torn, v, 

 p. 454 (1891). 



