166 MICROSCOPY FOR BEGINNERS. 



part of the lower or ventral flat surface ; back 

 convex, usually bearing spines, prickles, or scales. 

 Chcetonotus, II. 



a. Tail not forked, but often bearing finger-like ap- 

 pendages (J). 



5. Body entirely and finely ciliated, usually flattened. 



Turbelluria, III. 



6. Body smooth, without cilia, bristles, or spines ; tail 



pointed. Anguillula, IV. 



&. Body with bristles, podal spines, or both. Oligo- 

 chceta, V. 



I. CHIRONOMUS LARVA (Fig. 131). 



Chironomus larva has a worm -like, more or less 

 jointed, colorless body, eight or nine times as long as 

 wide, a large head, the mouth parts usually being dis- 

 tinctly apparent. The four short rudimentary leg-like 

 appendages are in pairs on each end of the long body, 

 the brownish hooks or strong curved bristles on their 

 extremities being more or less retractile, while two clus- 

 ters of long bristles spring from the upper surface near 

 the posterior border of the animal. The perfect in- 

 sect into which this larva will develop is a two-winged 

 fly resembling a mosquito. These are often seen in 

 great numbers above the ponds and marshes. The spe- 

 cies are very numerous, and have never been studied by 

 American entomologists. 



The eggs are very common on sticks, floating chips, 

 or other objects in the water. They are deposited in ft 



