G. S. Graham-Smith 
505 
miles away. Wasps came to these carcases in large numbers, 
occasionally in sufficient numbers to interfere with observation, and 
were seen feeding both on the flesh, when this was exposed, and on the 
fluids which escaped from the bodies. Under these conditions they 
must have become grossly contaminated with putrefactive and other 
bacteria. They also chased and frequently caught blow-flies, green- 
bottles and other flies, which came to the carcases. After removing 
its wings the wasp generally flew away with the body of the fly. Since 
flies are invariably contaminated, the wasps which catch and devour 
them must also become contaminated. Traps placed over the carcases 
of small animals caught them frequently. 
A number of observations were made on plums hanging on trees, 
in order to ascertain the species of flies which came to them. In the 
course of these observations wasps were seen both to eat the fruit and 
to catch the flies feeding on it. Investigations on the bacterial con¬ 
tamination of plums have been quoted previously (p. 495). In regard 
to fruit, however, experiments carried out by placing over-ripe fruit 
under a trap (p. 494) on the ground were the most instructive. Very 
large numbers of wasps were caught, on some days exceeding the flies 
in number. When the wasps and the flies reached the balloon trap 
the former pursued the latter, especially the various species of the 
genus Sarcophaga, and tearing them to pieces devoured them. 
Wasps also come into houses, especially into kitchens, in great 
numbers, and settle on all kinds of food. 
It is evident from their habits that the legs and mouths of wasps 
and their excrement must usually be much contaminated, but whether 
they are capable also of causing infection by regurgitating their food 
is not clear. 
These insects were more active than flies in cold, disagreeable 
weather, and were often caught in the traps, when few flies were about. 
It was noticed also that they were active earlier in the morning than flies. 
During the season 150 wasps were caught in the traps baited with 
excrement, 79 in traps baited with animal matter, and 973 in traps 
baited with fruit. Of the 1202 wasps caught in traps, 951 appeared to 
be V. germanica, 123 V. sylvestris and 128 V. vulgaris. 
Taking into consideration the extent to which they visit fruit, 
whether on trees or exposed for sale in shops, their well-known partiality 
for jam, sugar and other foods, and their liking for excrement, decaying 
animal matter and flies it seems very probable that they act not infre¬ 
quently as agents in disseminating pathogenic and putrefactive bacteria. 
