hungerford: anatomy of simulium vittatum. 377 



per cent chloral hydrate. Vaney, '02, finds that these tubes 

 pass from the larva to the adult without any transformation, 

 so that an examination of the larva gives a fair idea of their 

 position in the adult. Just caudad of the region where the 

 Malpighian tubules are attached, the hind gut takes a turn 

 dorsally to a point below the junction of the fifth and sixth 

 segments, and then bends caudad at right angles to about the 

 seventh segment where the tube becomes first constricted and 

 then dilated, especially on the lower side, which gives the ap- 

 pearance shown in r. p. fig. 2, pi. XLIII. This rectal enlarge- 

 ment is a transparent sac, the wall of which is distinctly 

 striated (see Fig. 3, PI. XLIII) and contains suspended from 

 its upper or cephalic end six cone-shaped papillse or glands, 

 the rectal glands (see Fig. 3, RP) . Each of these is made up of 

 glandular cells containing large nuclei. An examination of 

 the rectal pouch after treating it for some little time with 

 caustic potash shows not only the estodermal origin of the 

 papillae but the presence of tracheal filaments as well. 



Rectal papillae have been observed in a number of insects. 

 Chironomus has two, the house fly four, the stable fly four, 

 most Hymenoptera, Neuroptera and Orthoptera six, Lepidop- 

 tera 60-200, and Coleoptera and Hemiptera none.* 



Salivaru Gkinds. The salivary glands are a pair of organs 

 which lie in the fore part of the thorax on either side of but 

 dorsally to the oesophagus. (Fig. 4.) They are connected 

 with the common duct beneath the oesophagus by means of 

 slender ducts. (See Fig. 4, PI. XLIV.) They lie so close to the 

 prothoracic wall and so near to the large tracheal trunks of 

 the mesothoracic spiracle that they are often difficult to demon- 

 strate. They lie on either side, between the second oblique and 

 first longitudinal layer of muscle. Structurally they are in 

 two parts. There is an upper part, which when stained shows 

 itself to be glandular (see Fig. 4, PI. XLIV) and a nonglandular 

 part or sac. The glandular part is shown in sections to con- 

 sist of thick-walled pouches, the cells of which contain large 

 nuclei. In structure they resemble somewhat the acinous 

 glands figured by Packard (after List). They do not at all 

 resemble the trilobed glands of the mosquito or the slender 

 glands of Stomoxys. They appear to be somewhat similar to 

 those figured by Newstead for Phlebotmus. 



^ Miall ;ni(l HaniiiunKl. 



