420 THE ANIMAL PARASITES OF MAN 



hairs are of great service in distinguishing the larvae, 1 whilst in Culex the 

 number and position of the spines at the base of and on the siphon are 

 characteristic. The position assumed by the larvae in the water also varies 

 in the different groups ; most of the Anophelines lie horizontally, most of the 

 Culicina and ^Edeomyina hang head downwards. The pupae also vary, but 

 not to the same extent; the chief differences to be noticed are in the form 

 of the two respiratory trumpets. 



The eggs, which may be laid separately (Anopheles maculipennis, Stegomyia 

 fasciata, Joblotia nivipes, &c.), or in rafts (Culex pipiens, C. fatigans\ or 

 in chains (Tceniorhynchus fasciolatus\ present a great variety of forms. The 

 most peculiar are shown in fig. 273 (Mansonia, Culex, Stegomyia, Anopheles}. 



As in all insects they differ very materially in each species of one genus. 

 Those best known are the Anopheline eggs. 



The eggs always float on the surface of the water ; immersion soon 

 destroys them. 



Characters of Adult Culicidce. The chief characters by which true mosquitoes 

 or CulicidcB are known are the following : 



(1) Wings always with the veins covered with scales ; the longitudinal 

 veins usually six in number (in one genus seven) ; the costal vein carried 

 round the border of the wing. 



(2) Head, thorax and abdomen usually, but not always (Anopheles, &c,\ 

 covered with scales. 



(3) Mouth parts formed into a long piercing proboscis. 



As a rule the males may be told from the females by their antennae 

 being plumose, whilst in the females they are pilose (vide fig. 272', but this 

 does not invariably hold good, for in Deinocerites, Theobald, and Sabethes, 

 Desvoidy, and others, they are pilose in both sexes. The labial palpi are 

 very variable in regard to their form and the number of joints ; in the 

 Anophelina they are long in both sexes, as long or nearly so as the 

 proboscis, more or less clubbed in the males ; in Culicina, Joblotina and 

 Heptaphlebomyia, they are long in the males, short in the females ; in 

 jEdeomyina, short in both sexes. 



Scales. The most important structural peculiarities in CulicidFe are the 

 scales, which form the chief and most readily observed characters for 

 separating genera and species. 



The head, thorax, abdomen and wings are in nearly all cases clothed 

 with squamae of varied form, of which the following are the main types 

 (fig. 275) : 



(1) Flat, spade-shaped scales (a). 



(2) Narrow-curved scales (e). 



(3) Hair-like curved scales (d). 



(4) Spindle-shaped scales (/). 



(5) Small spindle-shaped scales (g). 



(6) Upright forked-scales (h and '). 



(7) Twisted upright scales (/). 



1 Recent information sent me by Dr. Grabham shows this statement to be not 

 quite correct, as the frcntal hairs may vary in different stages of the same larva. 

 This he has shown in Cellia albipcs, Theo., and I have ncticed it in a Nyssorhynchus 

 from Africa. 



