biPTERA OF MINNESO'TA. 



'Zo 



once notice that the insect is divided into three distinct parts, — the 

 head, the middle part or thorax, which bears the wings and legs, 

 and the abdomen, the latter composed of four visible rings or seg- 

 ments. The large compound eyes, composed of 125,000 facets, oc- 

 cupy the greater portion of the side of the head. A glance at Fig. 6 

 will show the appearance of a portion of the surface of the compound 



nProboscii (ensheuM in ttiepatfi) 



> > Satrellunjpirt^mesorkoTaxj 

 Hind leg. 



Tarsufi ] ' 

 (SjOintedjJ—i 



Fig. 5. Dorsal view (diagrammatic) of Tsetse Fly to show details of anatomy; from Austen's 

 "Monograph of the Tsetse Flies." The numbering of the veins of the wings and 

 the nomenclature of the cells differ from that employed by Comstock 1. a. Auxiliary 

 veil}; I first longitudinal vein; II, second longitudinal vein; III, IV, V and VI 

 are the 3d, 4th, 5th and 6th longitudinal veins respectively. A and B are respectively 

 the anterior and posterior transverse veins; C and D are the anterior basal and pos- 

 terior basal transverse veins. 



eye. Each hexagonal portion is called a "facet," and represents the 

 end of a tube, as it were, running down to nerve endings, which are 

 sensitive to light. There are, therefore, as many "tubes" as there 

 are facets. Fig. 7 shows a vertical section through a compound 

 eye ; c equals the cornea ; /, the corneal lens ; rh, the great rods or 

 rhabdomes, sometimes solid, but more generally tiny sacks filled 



