8i 



maxillae lie on their outer edge and somewhat dorsally. 

 At their tip they have spines and a membranous 

 lamella. The palps serve to close in the mouth cavity. 



(/) Labial Plate. Or under lip of Meinert, is a 

 conical toothed piece in the middle inferior line. 



This latter (and probably also the mandibular 

 teeth and maxillary hairs and palps) differs much in 

 different species (Fig. 28). It is generally of specific 

 but sometimes may be of generic importance. 



The Anal Pa-pillae. Note the tracheae ramifying 

 in these, the papillae being possibly gill-like in function. 

 In Megarkinus, Toxorhynchites, Mucidus, Psorofhora, 

 Lutzia, C. concolor, and C. tigripes they are quite 

 rudimentary. 



Culex. (i) Examine in a glass dish and observe 

 the hanging attitude of the larva and how the angle 

 varies in different species, e.g., in C. concolor it is nearly 

 horizontal. 



(2) Note with the microscope the absence of 

 palmate hairs. 



(3) Note the position and extent of the antennal 

 tuft, and shape of the antenna. The differences are 

 not so striking as in the case of the syphon. 



(4) By the great differences in 4 syphonic index ' 

 it is often possible to distinguish the different species. 



Important differences occur also in the scales of 

 the pecten and comb. It is possible to subdivide the 

 genus into groups in which these characters are more 

 or less alike. 



Stegomyia. The larva of Stegomyia is rather longer 

 than that of Culex. When disturbed it exhibits a 

 rather lashing movement like that of certain small 

 aquatic worms. When at rest at the surface, the 

 attitude of the body is almost vertical. The larva, 

 however, spends a good deal of its time browsing at the 



