84 



piece micrometer), and note great variation in 

 different genera and species. 



The Mouth Parts. — Note the characters of the 

 claw-Hke mandibles, and especially the exact 

 character of the triangular mental plate, which 

 forms a conspicuous dark triangular body on the 

 under surface of the head (Fig. 23). 



Note that in different species the plate varies 

 in appearance, especially in the size and number 

 of notches in its margin. In some species the 

 plate is like a shark's tooth, in others it is comb- 

 like. 



The Anal Papillae. — Note the tracheae ramify- ' 

 ing in these, the papillae being possibly gill-like 

 in function. In Megarhinus, Toxorhynchites, 

 Mucidus, Psorophora, Lutzia, C. concolor, and C. ' 

 ti gripes they are quite rudimentary. 



The Large Body Hairs. — These are long in 

 some larvae, much shorter in others ; their 

 arrangement is very similar in the different larvae. 



5. Cannabalism of Larvae. — Add some large 

 Culex larvae to a small bottle containing some 

 small larvae or Anopheles larvae. The Anopheles 

 larvae or small Culex larvae will be devoured by 

 the large forms. Mucidus sp., C. concolor, and 

 Psorophora sp., are especially cannabalistic. 



6. Observe the occurrence in nature of the 

 two forms, Culex and Anopheles, also what Culex 

 larvae are found living together. 



7. The Enemies of Larvae. — Add small fish, 

 waterbeetles, and their larvae (Dytiscidae, Hydro- 

 philidae), Libellula larvae, Corysca, Nepa, tad- 

 poles, and other water animals, respectively, to a 

 series of wide- mouthed bottles containing equal 

 numbers of larvae. Note the rate at which they 



