%l\t Canadian Intoutoloafet 



VOL. XXV. 



LONDON, AUGUST, 1893. 



No. -8. 



SOME INTERESTING COLOUR- VARIETIES IN THE GENUS 



CROSSIDIUS. 



BY H. F. WICKHAM, IOWA CITY, IOWA. 



While engaged in the re-arrangement of some boxes of Cerambycidai 

 recently, the peculiar modifications of the ordinarily very simple pattern 

 of coloration in the genus Crossidius brought about the desire to see to 

 what extent and under what circumstances certain of these modifications 

 were carried on or existent. The results of the studies ensuing thereupon 

 are presented in the present paper. 



The pattern which may be regarded as the typical one, and upon 

 which all the Others are built, either by simple addition or subtraction, is as 

 follows : — Head black, thorax black with yellow side margins, elytra yel- 

 low with the humeri and a large elongate common sutural spot black. I 

 do not wish it understood, however, that this is to be regarded as the 

 original pattern from which the others have been evolved through the 

 processes of natural or sexual selection — only as a common plan of 

 coloration, and one which forms a convenient standard of comparison. 



In habit the beetles are diurnal, frequenting flowers of golden-rod and 

 other yellow-flowered Composite, more especially in the arid regions of 

 the United States and southward. In our faunal limits the'genus is found 

 from Montana and Oregon to Texas and Southern California, spreading 

 over a vast extent of territory, and one of great differences in climatic 

 and atmospheric, as well as of geologic characters. Under these cir- 

 cumstances we might well expect to find the genus composed of either 

 many more or less closely allied species, or one or few very variable ones. 

 My own experience goes to show that, in this group, those species of 

 wide distribution offer many interesting variations, and to bring some of 

 these before the reader I have prepared the accompanying plate, wherein 

 the body and antenna? of the insects are represented in a conventional 

 manner, and all accuracy of delineation confined to the points under dis- 

 cussion — the elytral pattern. 



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