SCALES OF THORAX 73 



typical Culex. In Aedes squamiger and some other species the scales of the 

 upper series are broad and subtruncate and these are the " fan-shaped " scales 

 of Theobald. While in most species of Aedes the color of all the scales is dark, in 

 certain species there is a sprinkling of light-colored scales. This is also the case 

 with certain species of Psorophora, and in some species the scales are grouped 

 to form a definite pattern (P. discolor, P. signipennis) . 



In the genus Mansonia the scales of one series are more or less broadened with 

 a tendency to oblique truncation. This is the least marked in Mansonia fascio- 

 latus of any of the species we have examined and in it many of the scales are 

 hardly different from the " fan-shaped " ones above mentioned. These are the 

 so-called " Taeniorhynchus scales " of Theobald. In Mansonia titillans these 

 scales are differentiated most and very broad and asymmetrical and many of 

 them are shallowly emarginate at their apices. This constitutes the " Mansonia 

 scales " of Theobald. A similar type of scales, but with more rounded apices, 

 occurs in Bancroftia fascipes. Hardly distinguishable in character are the wing- 

 scales of Aedeomyia squamipennis, designated as " Aedeomyia scales " by Theo- 

 bald ; their angles are somewhat more rounded. 



Along the costal margin there is often a series of scales which are combined 

 into groups of several in such a way that they give the effect of stout spines and 

 this has led to the introduction of the term " spinose." The spinose effect is 

 produced by the crowding together of the pointed apices of several scales. Fre- 

 quently this spinose arrangement is hidden by overlapping broader scales. 



The head behind the eyes is covered with scales. The covering may be en- 

 tirely of broad scales lying fiat, as in Megarhinus, or there may be several types 

 of scales present. Very often there is an area of greater or less extent on the 

 vertex covered with " narrow, curved scales." In addition there is frequently 

 a mass of " upright forked scales " upon the vertex. These are narrow scales 

 with a long slender stem and expanded fan-like apically ; the apical margin is 

 roughly spinose, or it may be emarginate or tridentate. Transition forms may 

 occur between these and the other scales. Usually these " upright forked 

 scales " are in a dense mass on the vertex. In Johlotia and Lesticocampa they 

 are arranged in a long, regular, transverse row on the occiput. When the pro- 

 thoracic lobes are large the upright forked scales are absent. 



The thorax is more or less clothed with scales. This scale covering is least 

 developed in the lowest forms, the Anophelines. In these there is but a sparse 

 vestiture of hair-like scales upon the mesonotum, so that the integument itself 

 remains plainly visible. When the scale-covering is sparse the integument 

 usually shows peculiarities of coloration and it may be ornamented with spots, as 

 in many Anopheles and Aedes fulvus. The prothoracic lobes are usually more 

 or less scaled. There may be but a few loose scales or the lobes may be densely 

 covered with them. This latter condition is particularly true of the Sabethini 

 and other forms with large prothoracic lobes and the coloration of this vestiture 

 is often important for specific determination. The mesonotum is usually for 

 the most part densely covered with scales. In many forms a median depression 

 in front of the scutellum, the ante-scutellar space, is devoid of scales. The 



