120 Dr. IL Scott's Notes on biology of some inquilines and 



of the chamber walls, the space beinp; occupied by a narrow 



neck of thin membrane separating the two openings, as 



indicated in fig. 6 a. There is also a break in the thicker 



chitin of the rim of each chamber at the end remote from 



the aperture. The trachea is united to the chambers at 



the end beneath the orifices. No definite atrium has been 



discerned, the spiral thickening coming very close, if not 



right up, to the point of union with the two chambers. 



The thoracic spiracles are considerably larger than the 



abdominal, and differently orientated, though in their 



structure no difference from the abdominal spiracles has 



been observed ; in the thoracic the two chambers lie in a 



vertical direction with the orifices at the ventral extremity ; 



in the abdominal, the chambers he nearly parallel to the 



long axis of the body (or slightly oblique, with the front 



end a little lower than the hind), and the orifices at the 



anterior end. This orientation is best seen in specimens 



not treated with potash, viewed as opaque objects. After 



treatment with potash, the thin membrane within the 



chitinous ring tends to collapse, so that the spiracle may 



appear to rise from the bottom of a shallow crater. No 



difference from those of the full-grown larvae was observed 



in the spiracles of the youngest examples, so far as could 



be seen by viewing the latter as opaque objects. 



The spattjlate hairs (Figs. 1 a-c; 7 a, b). General 

 arrangement described above. In preparations in Canada 

 balsam, under a |-in. objective, the hairs bfirne by the 

 dorsal tubercles are seen to be flattened, transparent, 

 spatulate, and of varying size and length. Fig. 7 a shows 

 them in dorsal view. Fig. 7 b shows a series of the dorsal 

 tubercles in profile ; in optical section the cuticle appears 

 much thickened in the region of the tubercles, which seem 

 to be formed l>y the throwing of the cuticle into convo- 

 lutions; the minute erect processes (fig. 7b, pr.) spring 

 from the general surface of the cuticle. Even the long 

 slender setae projecting from the sides of the head and 

 body appear, under a |-in. objective, more or less flattened, 

 so that the difference between them and the spatulate 

 hairs seems to be one of degree only, not of kind. The 

 spatulate hairs recall similar structures figured and de- 

 scribed by Boving (3) as occurring on the hind margins of 

 the segments in the aquatic larva of Hydroscapha. 



The occurrence of these numerous tubercles and spatu- 

 late hairs can hardlv be connected witli life in bees' nests. 



