306 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



Sirex juvencus has been obtained in large numbers from the 

 same localities as those I mentioned for S. gigas. It has been 

 found in both Scotch and silver fir. The female is of a violet 

 bluish colour, as described and figured in Mr. Cameron's mono- 

 graph on the "British Phytophagous Hymenoptera." 



The males of S. gigas and S. juvencus are somewhat different 

 in colour from the descriptions and figures given in Mr. 

 Cameron's work. 



The head of the male of S. gigas has two yellow spots — 

 one behind each eye — as in the female. The antennae are 

 reddish yellow, the thorax black, and also the first two seg- 

 ments of the abdomen, except the sides of the second, which 

 are reddish yellow. The next five segments are reddish yellow 

 on the back, and more or less black underneath, although in 

 some these segments are all reddish yellow. The last segment 

 is black, and provided with a small, sharp, triangular projection. 

 The legs are usually black, with the joints and tarsus yellow. 

 In some, however, the femora only is black, and all the rest 

 of the legs reddish yellow. 



In the male of S. juvencus the antennae are black; the head 

 and thorax, very dark blue; the first two segments of abdomen, 

 violet blue; and the third one, violet blue on the upper side, 

 but reddish yellow underneath. The other five segments are 

 reddish yellow all over. The triangular projection on last seg- 

 ment is black and sharp at the point, The femora and tarsus 

 are reddish yellow, and all the rest of the legs black. One 

 very small male insect of half-an-inch in length has the last 

 five segments of abdomen yellow. It is evident that the males 

 of both species are variable in colour. 



I indicated in 1897 that the fly would probably be found in 

 many more of our woods, and I now find that this is the case, 

 as, so far as I have been able to ascertain, it has been recorded 

 from eight different counties in Scotland in addition to Bute, 

 although, so far, in very small numbers. In most cases it has 

 been obtained in twos and threes only, or, as in the case of 

 Inverkip, eight specimens. But from Bute and Arran of both 

 species more than one hundred specimens were obtained during 

 three seasons. 



