368 On Scent'Organs (?) in Female Midges. 



the seventh and ei'ghtli termites being nearly as long as the 

 abdomen, the otlier two pairs (between thefiftli and sixth and 

 sixth and seventli tei'o-Ites) a little over half as long. In 

 S. 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 ascertaiiied or confirmed in 

 all the above cases by pressin": the thorax and base of the 

 abrlomen of the flies between finger and thumb. A similar 

 test applied to various species of the genera Forcipomyia, 

 Dasi/helea, 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. annuh'pes, the only species in which I have so far been 

 able to search for them in the male sex. 



Apart from P. brachiaHs, the only species in which I have 

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

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

 observer! swarming with male mayflies of tlie genus Baetis, 

 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 somewliat increased 

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

 swarming in the normal manner. Whether the more elabo- 

 rate tubes of P. Irachialis 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 

 Lepidopteia and Trichoptera, and M. Tonnoir has recently 

 described them in certain species of moth-flies of the 

 genus Pericoma. In none of these cases are the lubes 

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

 and Bezzia. 



