1890.] President' 's Address. xxi 



with a velocity which baffles the eve of the observer, having the 

 appearance of a ruby or an emerald fleeting in space, they are generally 

 met with on flowers in summer days. 



Singularly enough, they always abandon the corolla of a flower 

 when another Hymenopteron alights on it. Could it be that they are 

 aware that they are held in abhorrence by other Hymenoptera on 

 account of their evil reputation which is so justly deserved. I do not 

 think so. Intelligence in insects does not reach that point even among 

 bees or wasps. The brilliancy of its coat would betray the Chrysis 

 anywhere. In truth, that coat of mail is extremely hard to perforate, 

 and the ruby -tailed fly can at will roll itself into a ball. Be it as it 

 may be, a Chrysis in possession of a flower abandons it the moment 

 another Hymenopteron alights on it. 



Unable to build or dig, the Chrysis must deposit her egg or eggs in 

 the cells of solitary bees and wasps. The larva must have animal 

 food. It will not touch the honey carefully stored by the mother of 

 its host. It will devour the host itself, little by little, of course, or 

 absorb the live provision intended for the young Sphex or Odynerus. 

 We are not quite certain which is the real process of the two in cells 

 containing stores of animal food. The result is the same. Either 

 starved or eaten, the host will never complete its evolution. 



I have before me my old wall close to the farmhouse. On one side 

 of the wall is a large cluster of tall fennel in blossom. On the rugged 

 and dilapidated surface are a dozen Chrysidae, the long-pedunculated 

 Pelopoeus, and two species of Odynerus unknown to me. The 

 Chrysidae go about quickly, but without that jerking motion so 

 peculiar to the Sphegidae and Ichneumonidae. They peer in every 

 hole, go half-way in, enter bodily at times, and are rather long in 

 coming out. Do these holes contain nests either partially finished or 

 partially stored ? We shall know very soon. There comes a wasp, 

 an Odynerus^ carrying something in its flight ; this is the provender 

 nothing less than the caterpillar of a noctuid moth. The place 

 is evidently inspected by the insect, which soars a little above 

 the entrance. There is nothing suspicious about ; the caterpillar and 

 the insect disappear in the crevice ; a short time after, the Odynerus 

 comes out and is off again. The entrance is not closed. A few 

 minutes later on the wasp comes back carrying another caterpillar. It 

 goes in again, remains longer than before, flies out afresh, and returns 

 with a pellet of clay, with which it begins closing its hole . Alas ! 

 you have left your door open ; have you not seen the parasites lurking 

 about the entrance ? The cuckoo has got into your nest during your 

 absence. You have striven hard to accumulate food for the main- 

 tenance of the grub which will issue from the egg which is the means 

 of propagating your species ; heap pellets of clay over pellets of clay 



