INSECTS
having the same essential structure as that of the horsefly (Fig. 170 A).
The house fly has no piercing organs; it subsists entirely on a liquid diet. The food liquid enters the aper- ture between the labella, and is drawn up to the true
Fig. 183. Head and mouth parts of the house fly.
A, lateral view of the head with the proboscis (Prb) extended. Ant,
antenna; E, compound eye; La, labella, terminal lobes of the pro-
boscis; Plp, maxillary palpi (the maxillae are lacking); Prb, pro-
boscis
B, the proboscis of the fly, as seen in three-quarter front view and
from below. The proboscis consists of the thick labium (Lb), ending
in the labellar lobes (La), between which is a small pote (a) leading
into the food canal (FC) of the proboscis. The food canal contains
the hypopharynx (Hphy), and is closed in front by the labrum (Lm)
mouth through the food canal in the labium between the labrum and the hypopharynx. The fly, however, is not dependent on natural liquids; it can dissolve soluble substances, such as sugar, by means of its saliva. The saliva is ejected from the tip of the hypopharynx, and probably spreads over the food through the channels of the labial lobes. These same channels, perhaps, also collect the food solution and convey it to the labellar aperture.
[ 346 ]
