litH.j 



51 



can divide all the 2 ? into two distinct groups, viz. i A — forms with 

 large and strongly excised hypopygium ; and B — forms with the 

 hypopygium entire and normal. Group A, according to present ideas, 

 is to be treated as one single " species," viz. : litterata, Geoffr., but it 

 includes forms of every possible variety in coloration ; in fact, their 

 coloui'-differeiices are much greater and more obvious than most of 

 those which, in group B, are treated as specific, (b) Then in group B 

 we find one form (excisa) separated from the rest by a characteristic 

 incision in the apical margin of its clypeus. But for distinguishing 

 inter se the forms, other than excisa, in this group, we can get but 

 little assistance from comparing them as to points of structure, and 

 are practically forced to rely chiefly upon colour-characters. Let us 

 now see what these characters are. 



I find it convenient for practical purposes to think of them as 

 divisible into two hinds, viz.: (1) Differences in the ground-colour ; 

 and (2) Differences in what has been called jrictura albida (velflava). 



(1) I think of the " ground-colour "in a TentJiredopsis as primarily 

 and originally pale yellowish or brownish, sometimes with a slightly 

 warmer reddish tinge (awantiacus) , but never definitely red. This 

 ground-colour is displaced by black (or at least dark brown), in some 

 cases to a very slight extent, in others largely, and in some almost 

 entirely ; and especially in the last case we find the blackening dis- 

 placed in its turn, but only in certain places, viz. : on segments of the 

 abdomen which lie beyond (i.e., posterior to) the " median segment" 

 or " propodeum " — by more or less extensive definitely red " macula) " 

 on each side of the upper surface or dorsum, which macula? are in 

 some species actually confluent over the dorsum, leaving only the basal 

 and apical segments entirely black. 



Accordingly, apart from pictura albida, we can arrange these 

 forms, according to their coloration, into a continuous series, with 

 practically quite yellow forms (e.g., typical nassata ? ) at one end of the 

 scale, and black forms with completely red-banded abdomens (e.g., 

 normal coqueberti ? ) at the other. Between these extremes we find 

 all sorts of intermediate conditions (e.g., forms darker and smaller than 

 typical nassata, but much resembling certain continental named varie- 

 ties of that species ; and black-bodied forms with hardly noticeable 

 red abdominal markings such as spreta, thornleyi, and the form called 



by British authors tristis). But I do not think that we have yet 



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