2 PEOCEEDIXGS OF THE NATIONAL MUSEUM vol.66 



different form from tliat of the Sarcopliagidae and are almost com- 

 pletely covered with very large chitinous spines. This button is 

 located on the inner edge of the spiracular plate either near the 

 middle or on the lower half. All of the pupae have a pit or cavity 

 at the posterior end which I call the " posterior cavity." There are 

 several species in the family Tachinidae which also have this 

 posterior cavity but all of these Tachinids have a definite button on 

 the spiracular plate. Within this cavity are located the spiracular 

 plates and they are always located on the upper half of the cavity. 

 It is very difficult to see these plat€s and it is also impossible 

 to determine a species accurately without first cutting into this 

 cavity. With a sharp knife and using a little care you can make a 

 transverse cut which will divide the cavity into an upper and a lower 

 half. After this operation the spiracular plates will be seen to be 

 very distinct in each species. In the pupal stage the tubercles on 

 the edge of the posterior cavity are quite variable in the various 

 species and may be present or absent and this is due, I think, to the 

 shrinkage in transforming and drying. However, the constancy of 

 these tubercles in their presence or absence seems to be reliable within 

 the species. 



In the larval stage the tubercles around the edge of the posterior 

 cavity are always present. The spiracular plate of the larva differs 

 slightly from that of the puparium. In the larva this plate is 

 generally a pale yellowish white in the central area with an amber 

 color towards the upper or outer ends of the slits and with a very 

 deep amber or dark brown ring around the edge. The ends of this 

 outer ring appear to be separated at the lower end of the plate. In 

 transforming to the pupal stage the appearance of the spiracular 

 plate is changed by the entire plate changing to a deep red or black 

 color, and in shrinking, the ends of this outer ring are contracted, 

 causing the plate to be a little more pointed. The slits are of an 

 amber color and darken a little in the pupal stage. The anterior 

 spiracles are often of considerable value, but there is a possibility of 

 variation in the number of lobes of each spiracle. 



For details of the terms used in this paper see plate 1, figures 1 

 fvnd 2. The dotted line shows the contour of the posterior cavity 

 and just above the horizontal axis is shown the location of the spi- 

 racular plates. 



I think the term spiracular plate is more appropriate and should 

 be used in place of the term stigmal plate used in my former paper.^ 

 The right spiracular plate is drawn for each species. 



I An illustrated Synopsis of the I'uparia of 100 Muscoid Flies (Diptera). by C. T. 

 Greene. I'roceedings of the U. S. National Museum, 1921, vol. 60, article 10, pp. 1-ct'J, 

 pis. 1-20, No. 2405. 



