armatures in the Hymcnoijtcrous genus CoUetes. 35 



intelligible the Tables now to follow, in which I do my 

 best to distinguish the $$ of such palsearctic Colletes- 

 species as are known to me by such characters only as can 

 he seen iviiltout dissection. 



I am bound to say at once, that I think we can hardly 

 expect quite satisfactory results from an inquiry which 

 begins by setting aside the most positive marks of differ- 

 ence which Nature has stamped on the creatures we are 

 endeavouring to distinguish. Therefore it does not sur- 

 prise me that, after attempting to deal with the matter 

 under such limitations, the results I have reached do not 

 even to myself seem very satisfactory. However, such 

 as they are, I will offer them to my readers. 



Apart from colour (including that of the pilosity, which 

 depends a good deal on the condition of the specimen, and 

 sometimes on other causes than that of specific identity), 

 the most conspicuous differences that I see between one 

 Colletes (t and another lie in {a) size; (]>) surface sculpture 

 of the body, especially its puncturation ; (r) the structure 

 and proportions of certain parts of the insect, especially 

 the head, the antennae, and the legs ; and perhaps also 

 in certain cases (d) the infuscation or the reverse of the 

 wings, including their nervures. 



Of these, the size of the insect is only in certain cases 

 of much use in " determining " it. The average size of 

 most species, when one is compared with another, differs 

 little ; and particular specimens in all of them may be 

 much larger or smaller than the average. Of course the 

 biggest namts is much smaller than the smallest nasufus ; 

 but out of a mixed lot of (say) succinctus, fodiens, montanus, 

 'jjicistigmct, and daviesanus, the biggest specimen and the 

 smallest might equally belong to any of the species. 



The sculpture-characters are much more to be trusted, 

 but they are extremely difficult to describe in unmistak- 

 able terms: — e.g. such an expression as "fine punctur- 

 ation," a " close puncturation," conveys different ideas to 

 different minds, and even to the same mind at different 

 times. Each reader measures such expressions by a 

 standard of his own, and even that standard is liable to 

 vary. 



In the shape and relative proportions of the head, etc., 

 we do at last arrive at characters which can be stated 

 'positively. But even here, it is surprising how difficult 

 it is to be quite sure that one sees what one thinks one 



