1890.] President's Address. xxvii 



and the fly is fixed under the abdomen, although still held by the 

 mandibles while the rakes are at work. Now is the time ! As quick 

 as lightning one Tachynaria, sometimes two, is on it. The deed is 

 done. An egg has been deposited, glued, along the corpse ; from that 

 egg will issue a grub, a messmate of the young Bembex, and the 

 mother must needs increase the number and size of her supplies to 

 feed her progeny and the parasites which she has been instrumental in 

 bringing into her nest. 



Fabre has justly said that the Bembex is perfectly aware of the 

 presence of the flies lurking about her nest. She shows it by a shriller 

 sound than usual when she perceives the flies too near the entrance.. 

 I have also seen her darting away with her burden and coming back 

 again ; poised in the air above her burrow, she takes another survey ; 

 the flies are there still, they take good care not to move away ; they 

 know, of course, that the mother must enter ; she is aware that her 

 progeny is perhaps waiting for its dinner ; are not the inner parasites 

 also waiting ? 



Now, here is an insect which preys on flies of different varieties, for 

 the debris of the nest prove that clearly, and which has not the 

 common intelligence to pounce upon the Tachynariae. She sees the 

 parasites increasing daily in size and numbers, and it is solely by dint 

 of heaping daily a larger quantity of food that she will keep them 

 from attacking and devouring forsooth her young. 



The only explanation I can suggest is that she preys on flies only ; 

 the grubs are repugnant to her. 



These Tachynariae are not parasites of the Bembecidae only. I 

 have already told you of that Odynerus whose galleries were so often 

 visited by the Chrysidae. That unfortunate wasp is_ perhaps more 

 than any other I know victimized by parasites. From that dilapidated 

 wall where I first discovered it I got no less than nine kinds of these 

 deceitful ruby-tailed flies. The Tachynaria was there in plenty 

 manoeuvring in the same way ; a sudden dart and the fly is again on 

 the wall, and looking most innocent. However quick the movement,, 

 the egg has been glued on the body of the Noctuid caterpillar, and 

 what with the visit of the Chrysidae, the eggs of Tachynariae, and 

 the singular nymphal case I see protruding from a hole, the young 

 Odynerus will have no easy time of it. 



It is the first time that I have seen this sheath. It is nothing else 

 than the nymph of a fly — either a Bombylius or an A?ithrax. That 

 old wall is indeed a great friend to me ; often have I seen Anthrax 

 (Exoprosopa) venosa alighting on it. Too much preoccupied with 

 the Chrysidae or the two Odynerus which tenant it, I had hardly 

 taken notice of this elegant insect. I should have remembered that 

 the European A punctata is a parasite of an Osmid, Heriades trun- 



