74 ARTHROPODS 



ing it on a slide, and put it under the lens of the dissecting 

 microscope or the low power of the microscope without a 

 cover glass. Look for the antennae. When you find them 

 remove one with a scalpel and tweezers. 



Make a drawing of the head as it appears from the front. 



Draw one of the antennae. Draw longitudinal and lateral 

 axes. 



(2) Find the tongue bent back under the head. Straight- 

 en it out and examine the joint. Seize it carefully with the 

 tweezers, and pull it out. Put it on a slide properly spread 

 out and put over it a cover glass. Examine under low 

 power. Note the shape, markings and structure. 



Find the following parts : 



a. The main shaft, the tongue, is divided into two spread- 

 ing parts, the labial palpi, at the end. Do you find the parts 

 smooth or rough ? Is there a system of projections? What 

 is their arrangement? These are tracheal tubes and serve 

 to keep the tongue well spread. 



b. On the head near the base of the tongue find two slen- 

 der projections, the mandibles, which are small in this species 

 and almost undeveloped in the male, but are very prominent 

 in the females of the mosquitoes and horseflies. 



c. The jointed, hairy, maxillary palpi on the shaft of the 

 tongue. 



Draw proboscis of fly enlarged. 



The Thorax. — (i) How many pairs of legs? Where 

 attached to the body? How many fully developed wings? 

 Behind the wings is a pair of membranes, the alnlcts. Are 

 these attached to the wings or are they separate? 



(2) Under the alulets are a pair of small white appen- 

 dages ending in a knob. Where are they attached to the 



