1909J 133 



which they im mediately settled down, the Female beini,' then in 

 possession of the prey. As in E. livida, the male hangs by his two 

 anterior legs to a leaf or grass-stem, supporting the whole weight of 

 the female, with his intermediate legs tightly pressed to her thorax 

 and his posterior |)air clasping her abdomen. The female is all the 

 time squeezing and kneading the prey, and every now and then 

 thrusting her proboscis into a fresh place, apparently in order to 

 extnict all the juices from its body. Many pairings were witnessed, 

 the male in every case providing the prey. In some minor details the 

 habits of this species differ from those of E. horealis and E. livida, as 

 recorded in this Magazine.* It differs more particularly from the 

 latter species, in that instead of the females dancing together and so 

 attracting the males, the males of E. opacn, always provided with 

 prey, fly with a very rapid erratic zigzag flight over and about the 

 low plants. They thus appear as it were to advertise themselves, 

 and induce the females to take flight also. As soon as this happens 

 ihe female is at once chased and pairing takes place as above de- 

 scribed. So far as my observations go, copulation only occurs during 

 sunshine, whereas in E. livida it is in the evening or late afternoon. 

 I kept the insects under continual observation from one until 

 four o'clock, but at 3.15 p.m. the sun disappeared, and from that time 

 onwards [ did not see another individual of either sex on the wing, 

 although there were scores settled about on the low herbage. I also 

 failed to find even a male with prey. In the course ol" these observa- 

 tions, while closely watching a male and female in copula quietly 

 settled upon a grass stem, I saw the male uncouple and fly away. At 

 the same moment the female dropped the remains of her prey and 

 flew away also. If this should prove to be the usual procedure, we 

 can understand why the female is never at any time seen with prey 

 except during the act of copulation. The observation at the same 

 time supports the suggestion raised by Mr. Hewlett in his admirable 

 paper on E. horealis, that the provision of prey at this particular time 

 is a physiological necessity for the proper performance of the act of 

 copulation. If the prey be absolutely necessary to the female through- 

 out the act, we can at once see why it should be invariably provided 

 by the male. Professor Poulton has pointed out to me that if the 

 prey is a physiological necessity for copulation, it by no means follows 

 that it is of value as food. Its importance may depend upon incidental 

 or correlated movements of limbs, or of internal structures. L'hrough- 



VoL xliii, p. 229, and VoL xliv, p. ISl. 



