368 On Scent-organs (?) in Female Midges. 



the seventh and eighth tergites being nearly as long as the 

 abdomen, the other two pairs (between the fifth and sixth and 

 sixth and seventh tergites) a little over half as long. In 

 B. ornata, Mg., there is apparently only one pair of tubes, 

 between the seventh and eighth tergites ; these are colourless 

 and not much shorter than the abdomen. 



The presence of the tubes was ascertained or confirmed in 

 all the above cases by pressing the thorax and base of the 

 abdomen of the flies between finger and thumb. A similar 

 test applied to various species of the genera Forcipomyia, 

 Dasyhelea, Kempia, Culicoides, and Stilobezzia failed to pro- 

 duce any eversion, so that it is likely that the tubes occur 

 only in the bare-winged group. Up to the present I have 

 found them in females only ; they are absent in the male of 

 B. annulipes, the only species in which I have so far been 

 able to search for them in the male sex. 



Apart from P. brachia/is, the only species in which I have 

 observed the females swarming is P. fiavipes, Mg. This was 

 at Snailbeach, Salop, in July last, where a few females were 

 observed swarming with male mayflies of the genus Ba'etis, 

 on which the Palpomyia were preying (see Ent. Month. Mag., 

 Sept. 1920). Although the suggestion may seem fanciful, 

 it is perhaps within the bounds of possibility that in this case 

 the tubes were of advantage on account of their slight resem- 

 blance to the tails of the mayflies, thus rendering them more 

 easy of capture. The possibility of this is somewhat increased 

 by the fact that in this species I have also observed the males 

 swarming in the normal manner. Whether the more elabo- 

 rate tubes of P. brachialis have been developed through the 

 addition of some sexual function, or whether (more probably, 

 perhaps) the function is connected with sex in all cases, can 

 only be determined by careful observation of the habits of 

 allied species. 



So far as I am aware, eversible tubes have not hitherto 

 been found in any Chironomid, nor in the female of any 

 insect. They are, of course, well-known in the males of some 

 Lepidoptera and Tiichoptera, and M. Tonnoir has recently 

 described them in certain species of moth-flies of the 

 genus Pericoma. In none of these cases are the tubes 

 situated at the end of the abdomen as they are in Palpomyia 

 and Bezzia. 



