8 
Wabble Ely. 
continued (see fig. 5, p. 7) to be that of a pair, of short horny, some¬ 
what bent cylindrical, or partially cylindrical, tubes, covered at the 
end (fig. 6) with round or oval discs, which appear to have a definite 
narrow border, and across the centre of the disc to be of a sieve-like or 
spotted appearance. Fig. 7 precisely represents the appearance when 
Fig. 6. Fig. 7. 
Fig. 6. —Spiracle-tube (one of Ihe pair), much magnified. Fig. 7. —Discs at 
extremity of spiracle, as seen with quarter-inch object-glass. 
much magnified. These discs may amount to as many as about six- 
and-twenty on each spiracle, and appear to me to be placed each at 
the extremity of short cylinders. Whether the spotted or sieve-like 
appearance is caused by minute hairs placed so to preserve the delicate 
tubes from the entrance of foreign bodies, I had not sufficiently high 
microscopic powers to ascertain. Up to the time when the moult takes 
place to the final form, these spiracles were in all the specimens I 
examined buried up to their disc-covered tips in the tail-end of the 
Fig. 8. —Spiracles fully developed, magnified. 
maggot; then they are cast entirely with the moulted skin, and in the 
newly exposed surfaces beneath we find the first appearance of the well- 
known kidney-shaped spiracles (see fig. 8), but (in the specimens I 
examined) with the surface somewhat more radiated, and the colour of 
a paler chestnut than in their later condition. 
The changes of condition appeared to be rapidly gone through, 
and it was when the maggot has gained about a quarter or third of 
