350 



INTRODUCTION TO ZOOLOGY 



with serpentine bends, but without the complicated twists of 

 a Harlequin. Like the latter, this larva makes mud-tubes, 



but it leaves them very fre- 

 quently. The head bears a 

 pair of antennae that can be 

 completely withdrawn within 

 it. The first segment of the 

 body bears a pair of hooked 

 structures fused at the base, 

 and the last segment bears a 

 similar pair, but larger and 

 widely separate in this case. 

 In all these, the circlet of 

 hooks can be withdrawn 

 within the soft flesh, and in 

 swimming the hind append- 

 ages move with a quite 

 regular stroke ; their tips 

 and the hooks being first 

 indrawn and then suddenly 

 shot out again, separating as 

 widely as possible. The 

 fused appendages in the first 

 segment are used chiefly 

 when moving over a surface, 

 when the whole body seems 

 to be pulled and hitched 

 forward on them as on a 

 kind of crutch. The last 

 segment bears four little gills 

 and two other processes, each 

 having on it a bunch of stiff 

 hairs. 



egg cluster: 



The Pupa. 



The pupa also 

 is aquatic, and re- 

 sembles that of gnats, having 

 much the same shape, and a 

 similar pair of respiratory 

 tubes on the thorax. It is, 

 however, of a paler yellow- 

 brown colour ; also it generally rests below the water, appar- 



FIG. 272.Tanypus (larva). 



, Fused front appendages ; Z 2 , back, hooked 

 appendages ; g, gills. Egg cluster is x 2. 



