MORPHOLOGICAL CHANGES OF STEGOMYIA FASCIATA. 



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difficulty seen to be not quite simple ; in later phases they are sub-plumose and may 

 be subdivided into a number of branches. In the first three phases these long hairs 

 are found on the first five segments, those on the earlier segments being the longer and 

 stronger ; in the last phase they are present on the first eight abdominal segments, 

 those on the first and second segments having several branches, those on the third 

 and fourth being triple and those on the other segments being double. The degrees 

 of division of the hairs is, however, variable. 



The siphonal, sub-siphonal, and anal plumes are all single simple hairs in the first 

 phase, but in subsequent stages they undergo division, this being especially marked 

 in the case of the sub-siphonal plume, which in the fourth phase may be composed of 

 certainly six sub-plumose branches. 



Fig. 5. Luiva of Slegoniijia fdscUUa ; 1, II, 111, IV, scales from the comb iu the four 

 stages ; I', II', 111', IV', scales from tlie pectcn in the four stages. 



Comb (fig. 5). The comb in each phase consists of a single row of barbed scales, 

 not easily seen in the young larvae on account of their pale colour, but conspicuous, 

 dark, and highly chitinised objects in more developed individuals. The number of 

 scales varies considerably both in the same individual and in different larvae at 

 the same stage of development. In the first phase there may be 4 to 6 scales, in the 

 second 8 to 10, in the third and fourth about the same number, and sometimes as many 

 as 12. The most notable change is that which occurs at the time of the first moult, 

 when the number of scales doubles, and in later phases, although the number may 

 remain constant, it does not again return to that found in the first phase. 



In addition to an increase in size and strength, the individual scales undergo a change 

 of form during development. At every stage they bear numerous barbs, the number 

 varying greatly, both according to the individual and to the position of the scale iu the 



