302 



APPLIED ENTOMOLOGY 



The mouth parts of flies are for sucking, and in some cases for piercing, 

 also. True " biting flies" do not exist, the "bite" being really caused by 

 the plunging of the sharp-ended, piercing mouth parts into the object 

 attacked. There seems to be little doubt that the mouth parts of flies have 

 been derived from ancestors with chewing structures, but the changes 

 have been so great that to identify the different pieces with the corre- 

 sponding ones of chewing insects is very difficult, and different views on 

 this have been advanced by students of the subject. 



FIG. 319. Mouth parts of A, a Tabanid; B, a mosquito: a, antenna; au, compound 

 eye; hp, hypopharynx; Ibr, labrum; md, mandible; mx, maxilla; mx2, labium; oc, ocellus; 

 pm, maxillary palpus. (Modified from Laug's Lehrbuch.) 



Without going into details, it may be stated that in the more typical 

 fly mouth parts there are six bristle-shaped structures enclosed by a 

 sheath, and one pair of segmented palpi (Fig. 319). The sheath is 

 generally regarded as representing the labium or hinder lip, while the 

 bristles represent the front lip or labrum, the tongue or hypopharynx, 

 the two mandibles and the two maxillae. At the outer end of the sheath 

 is a pair of lobes, often large, and these are considered as the labial 

 palpi, leaving the segmented pair to represent the maxillary palpi. 

 In some cases, the surfaces of the lobes regarded as labial palpi are 

 roughened and adapted to the rasping of surfaces. Bringing together 

 certain of the bristle-like mouth parts forms two tubes, or, in some cases, 

 grooves more or less completely closed, through which fluids can be 

 drawn into the body, and saliva be led into the wound made by the 

 tips of the bristles. Solid food is utilized only by first dissolving it in 

 saliva. 



