fig [March, 



A RIBBON-MAKING FLY: 

 THE OVIPOSITION OF CERATOPOGON mxiDUS Macq. 



BY A. H. nAMM, F.E.S, 



For a few days last August I was spending part of my holiday at 

 the picturesque little village of Woolhampton, near Newbury, Berks. 

 The evening of the 13th was very warm and sultry, and the various 

 "biting" flies, such as Anopheles, Culex, Ceratopogon, and Simulium, 

 were feasting upon all and sundry. I often had three or four Culex 

 pipiens on my hand at one time, but, fortunately for me, their " bite " 

 leaves no after-effect. 



I was patiently watching, on the bank of a stream running through 

 one of the numerous osier-beds that are such a feature of this part of 

 the Kennet Valley, several species of Hilara, esjiecially H. lurida and 

 S. niqrina, the males of which were very busy catching their " prey " 

 and afterwards going through their usual courtship tactics. It was 

 while thus occupied that I noticed, hovering above the surface of the 

 stream, a fly that had something white hanging beneath it. Thinking 

 it was another species of Empid with " prey," I netted and boxed the 

 fly, and then recognised it as a Ceratopogon. I then made a hasty 

 examination with a lens of the object which the fly had dropped in the 

 net, and was surprised to find it was a gelatinous ribbon of ova. I then 

 saw and netted several other flies hovering over the stream, with similar 

 ribbons. They hovered (with little or no perceptible movement) about 

 two feet above the stream and then immediately began the work of 

 ribbon-making. By patiently watching one could observe the operation, 

 occupying about three minutes, from start to finish. Gradually the 

 ribbon, hanging vertically from the very start, would lengthen, until 

 the full number of ova had been extruded. I could not determine 

 whether the legs contributed in any way by holding and paying out the 

 ribbon during its extrusion ; for nearly all the flies kept in mid-stream, 

 and the light, just before sunset, was none too good. When its full 

 length was attained the fly, still poised motionless in the air, dropped the 

 ribbon into the stream beneath, where it gradually sank as it was borne 

 along by the fairly i-a,pid current. 



The following measurements, for which I am indebted to my friend 

 Dr. Eltringham, were made from a dry and probably shrunken ribbon, 

 which, moreover, was not of maximimi length, as the fly was netted 

 before its completion : — 



Length of ribbon, 19 mm. Width of ribbon, "22 mm. 



There are 30 ova per mm., making 570 ova in all. 



