BY JOHN L. FKOGGATT. 659 



throughout the body. Absorption will, in all probability, take 

 place slowly through the skin; l)ut the action of some liquids is 

 far too rapid to admit of this happening, so that, in these cases, 

 attention must be paid to the openings into the body. I am not 

 at present in a position to point out more than the possibilities 

 of this point, but it is receiving further attention. 



The absence of pores in the skin of the maggots of these species 

 is extremely interesting as well as curious, because the larvae of 

 most other insects, and even diptera, show definite, well-marked 

 pores. 



The anterior and posterior spiracles are totally different from 

 one another, the most marked specific differences being given by 

 the latter. 



The anterior spiracles are situated one on either side of the 

 body, on the first thoracic segment. In shape, thev resemble a 

 cap with "a sharp upper edge, and a row of tassels along this edge. 

 The caps are chitinised pi-ojections of the two main tracheie on 

 wliich they fit Ijy a thickened ring; and it is from this demarca- 

 tion-line that all measurements are taken. In some species, the 

 cap is differentiated into a thicker lower part, and a thinner 

 upper part. The tassels or tubules are hollow, the open ends 

 ha\'ing a much-strengthened chitinous rim to keep the apertures 

 open. The number of tubules varies in different species, and 

 within certain limits in the same species, and even between the 

 right and left anterior spiracles in the same maggot. 



The tracheae terminate posteriorly on the anal segment in two 

 spiracular plates or stigmata, the posterior spiracles. These are 

 slightly raised above the sui'face of the truncated end of the 

 maggot. The position of these plates on the body is such that 

 the bases of the plate, l.t^., the spaces in the band, point obliquely 

 tow^ards the median perpendicular plane of the body, and with 

 the median horizontal plane of the body passing through the 

 lower portion of the plates. 



As both spiracular plates are alike for each species, a general 

 description of the characters of one will serve equally for the 

 other. 



