13° 



MORPHOLOGY AND TAXONOMY OF ADULT MALES 



to width 1-3-1-4 (1-38) : 1, and the ratio its length to the total body length 1 : 10-2-12-0 (n-o). 

 Basal ridge of penial sheath and its projection well developed ; process of penial sheath well 

 pronounced. Aedeagus gradually pointed. Setae of genital segment : Dorsally, 3 setae always 

 present on each side near the base of the style ; ventrally 3-4 (3-7) setae occur on each side 

 of the penial sheath, and 4-5 (4-3) setal sensilla on its process. 



Material : 10 specimens examined, collected by myself, on beech trees (Fagus 

 sylvatica), in the Imperial College Field Station, Silwood Park, Sunninghill, Berk- 

 shire, England, iii-iv.1964. 



Remarks : Although the present study is mainly concerned with morphology and 

 taxonomy, some biological observations were also made. According to Blaire 

 (1958), the second stage larvae of this species, usually males, migrate from the 

 small twigs towards the main branches and trunk of the trees between February 

 12th and April 10th ; however, the writer was able to produce adult males from 

 larvae collected during the last two weeks of April. It was found that the second 

 stage larvae take about 48 hours to reach the third stage, and the latter about 

 another 48 hours to become prepupae ; the prepupae take about 7 days to develop 

 to pupae, and the pupae about 8-10 days to produce males with well developed 

 antennae, legs and wings, but still in a stationary condition or with very limited 

 movement. The males became active after about 48 hours, after which the long 

 waxy tassels covering the abdominal segment VIII were produced ; they were 

 then ready to emerge from their puparia and search for the females. The males 

 mated 5-10 times with females introduced to them in the same glass tube ; each 

 copulation usually lasts 1^—3 minutes and may be repeated with the same female 

 or another one at variable intervals from several minutes to a few hours. The 

 males fly in rapid and rather short jumps (a few inches), and all died within 72 hours 

 from their emergence. 



200^- 



100^- 



Fig. 20. Trionymus newsteadi (Green), lateral view. 



