460 
DISCURSIVE NOTES ON THE 
their attentions entirely to spiders — even the very largest 
‘ tarantulas ’ that burrow in the ground are not immune. 
The process of excavating a burrow is essentially the 
same as in the Sphegidce, and carried out with the same extra- 
ordinary vigour. But, speaking from memory, I have found 
the Pompilidce to work silently. 
When the time comes for filling up the burrow and ramming 
down the earth, however, the Pompilidce show an extraordi- 
nary difference from the Sphegidce in their methods. As was 
said, a Sphegid uses the front of her head, with steady pressure, 
to ram in the earth ; but a Pompilid does exactly the opposite. 
Standing over the mouth of the burrow, she puts down her 
tail and uses it to press down the earth — sometimes with slow, 
steady movements. In one case that I observed, however, 
a series of quick blows was struck, the Pompilid throwing 
her whole body into such rapid vibrations that her outline 
was blurred, and she reminded one of the operations of 
a pneumatic riveting-hammer. This difference between the 
two closely allied families I have found so invariable that 
if I were asked whether a given specimen were Sphegid or 
Pompilid, I should say : ‘ Let me see it filling up its burrow, 
and I will tell you ! ’ 
A unique and remarkable observation that fell to my lot 
seems to indicate that not all Pompilidce make burrows. I 
saw, in Tero Forest, a medium-sized typical blue-black specimen 
pounce on a spider, lay an egg upon it, and depart. The 
spider did not seem to have been stung at all, and it would 
seem as if this aberrant Fossor had lost its instincts of bur- 
rowing, and merely laid its egg on the surface of its living 
prey, as do the parasitic Tachinid two-winged flies. 
With these notes I will conclude these discursive remarks ; 
but enough has been said to show how many subjects are 
embraced by the study of these fascinating insects — *to my 
mind, far more attractive than their much-belauded relatives, 
ants and bees. 
The questions of Instinct or Intelligence, of Natural 
Selection and the Struggle for Existence — the colours of insects 
made intelligible by the former, and their destruction by 
enemies exemplifying the latter — have all been touched upon. 
