AMINO ACIDS 99 



but one of these spots there were detectable quantitative differences. 

 In addition there were seven spots pecuhar to males and two spots 

 peculiar to females. Some of these spots were probably the pteridines 

 mentioned in Chapter 4. 



Although Fox was not immediately concerned with potential 

 systematic applications stemming from his work, it is possible that 

 the comparative biochemistry of sex, could be extended profitably to 

 other species and genera, or even higher taxa, of insects. In the 

 present case a number of absolute sex-linked differences were re- 

 corded in one species, and a systematic extension of this comparison 

 could hardly fail to provide valuable insight into relationships. 



Micks (1954) applied amino acid chromatography to a study 

 of certain mosquito species which are difficult to separate on morpho- 

 logical bases, and his illustrations of chromatographic differences are 

 convincing. Later, Micks (1956) studied several different groups of in- 

 sects, and again his illustrations of comparative ninhydrin patterns 

 show distinctive differences at the order level (that is, in a compar- 

 ison of certain Hemiptera, Diptera, and Orthoptera). Even three 

 genera of cockroaches could be distinguished chromatographically. 

 Within a single genus, however, any differences which were apparent 

 were quantitative. Intrageneric qualitative differences in mosquito 

 (Culex) had previously been reported by Ball and Clark (1953). These 

 investigators found aspartic acid in Culex quinquefasciatus and C 

 stigmatosoma, though an extract five times as concentrated was used 

 in the last named species. They also reported the unusual sulfonic 

 amino acid, cysteic acid, in C tarsalis and C. stigmatosoma but not 

 in C. quinquefasciatus. Cysteic acid may possibly have arisen as an 

 artifact by oxidation of cysteine. It is noteworthy that specimens of 

 C quinquefasciatus as widely separated as California and Texas were 

 qualitatively identical, and Ball and Clark concluded that the inter- 

 specific differences were intrinsic, not environmental. 



In other systematic zoological studies involving chromatog- 

 raphy, Kirk et al. (1954) found that seven species of land snails could 

 be distinguished by their fluorescent patterns. The pattern for a 

 given species was the same regardless of diet or geographical location. 

 A few other reports are scattered throughout the literature such as 

 those of Mohlmann (1958) who studied fluorescent patterns of butter- 

 flies and Wright (1959) who studied mollusks of the genus Lymnea by 

 similar methods. In summary, however, in the judgment of the 

 present writers none of the papers in this series extends beyond the 

 point of suggesting that chromatographic studies might be valuable 

 in future taxonomic investigations. None was addressed to any 

 specific problem or shed any light upon an actual systematic problem. 



