ENTOMOLOGY

COMMON FI.IES AND HOW TO TELL THEM APART 145parts with a tiny papilla on each side (fig. ~O) and there is but onegreat hook. The anterior spiracles (fig. ~l) show six or seven lobes;on the under side of the sixth and following segments there is a transverse,swollen area, wider in the middle and somewhat pointed towardeach end. These areas are provided with minute teeth.. The area isslig_htly prominent and shows two approximate processes. The stigmalfield is barely if at all conCave and not outlined by tubercles; the posteriorspiracles (fig. ~2) are prominent, less than their own diameter apartand each with three winding slits and a button at the base. In somecases two of the winding slits are apparently connected. The secondstagelarvm has two straight slits in each stigmal plate, while in the firstlarval stage there a.re two sma.ller slits on a tubercle each side of theFIG. gO (left).-Larva of Mlruca domestica; dorsal view of head and porthorax. (Greene.)FIG. 21 (center).-Larva of Mwca dOm6Btica; lateral view of tenninal segments.(Greene.) The spiracles are located on the eighth abdominal segment. The ninthand tenth segments are ventral and not very distinct, enclosing the anus.FIG. 22 (right).-Larva of MUllca dOm6l1tica; enlarged sketch of right stigmal plate.These plates are less than their breadth apart. (Greene.)middle and in this stage there are no anterior spiracles. (See ChapterVIII.)The larva of the house 1Iy is rarely swallowed, but there are recordsto that effect. It sometimes breeds in decaying fruits and vegetables.The principal breeding place is in horse manure. It also breeds in humanexcrement and because of this habit it is very dangerous to humanbeings.StomOITJ'!J8 c;alcitrans LinnreusThe larva of this species is very similar to that of the house 1Iy, witha single great hook; the anterior spiracles have five lobes (fig. ~S); thesixth and following segments have each an area on the under side providedwith tubercles; this area is wider in the middle; anal area has twosubmedian tubercles and three each side of these; above them is a row