122 ELEMENTARY LESSONS ON INSECTS 



On the thorax note: 



1. The few veined, transparent and highly efficient wings. 



2. The knobbed halter es that replace the hind wings on 

 the metathorax. 



3. The slender tarsi whose end segments bear sucking 

 pulvilli, that adhere to very smooth surfaces. 



II. With a maggot in hand, note. 



1. The soft-skinned body, wide in the rear and tapering 

 forward to a pointed front end. 



2. The absence of head and of all external head appendages 

 of the usual sort. 



3. The mouth hooks, a single pair laid parallel, brownish 

 or blackish in color, strongly chitinized and hooked 

 downward at the tips, retractile, adapted for tearing 

 up tissues to liberate their juices. 



4. A pair of small spiracles at the rear of the prothorax — 

 one each side. 



5. A pair of larger spiracles on the blunt rear end of the 

 body, opening to rearward. 



6. Longitudinal air trunks inside the body (more or less 

 visible through the transparent skin) connecting with 

 the spiracles, and sending branches in to all the tissues. 



7. A dark colored alimentary canal extending lengthwise 

 through the body. By looking inside the body of the 

 larva great masses of white fat may be found filling 

 the greater part of the body cavity. 



