INVESTIGATIONS ON THE MUTILLID WASPS 7 



On the top of one of the latter the Mutilla was seen. It remained still a few 

 seconds, then precipitately vanished beneath a lump of earth, as is their habit 

 when alarmed. In a few minutes it came out into the open again cautiously 

 and, after examining with its antennae some pupae near the one on which I 

 had first seen it, started, with its head facing the tail end of the pupa, to 

 whittle away with its jaws at a point midway between the two poles with 

 such energy as to rock it. Its antennae were crossed and below its head. 

 After five minutes' work in the horizontal position it gradually raised itself 

 vertically, with its head down on the pupa, supporting itself against the 

 side of the jar, so that a full view of its movements with a lens could readily 

 be obtained. Extremely fine movements of the jaws in and out took place 

 with great rapidity and with such delicacy that unless one's attention had 

 been attracted by corresponding movements of the labial palpi the operations 

 in progress would have been undetected. From time to time a sharp turn 

 of the head through a quarter of a circle on each side also went on. 



After half an hour's work the Mutilla retired a short way from the 

 pupa and, resting on its side, cleaned its antennae and rubbed its legs together, 

 but then manifested some uneasiness at the light, for at this point I had to 

 watch it by lamp liglit, and concealed itself. But when the light was very 

 much shaded it returned to the pupa, put its head to the site of its previous 

 operations, where with a lens I could see a small breach of surface, and then 

 gradually raising the hinder part of its body so as to rest again on its head, 

 recommenced work, its antennae being this time in front of its head, but resting 

 on the pupa. Occasional movements of anteflexion of the abdomen then took 

 place, as if the insect were preparing for oviposition, and finally, after at least 

 an hour's work, the insect resumed the horizontal attitude on the pupa, and 

 having examined its work advanced so that its hinder end came somewhere 

 over the breach. It then moved to and fro, feeling for the exact spot, and then 

 remained still, doubtless in the act of oviposition, running away a few seconds 

 later. 



Though the female worked so indefatigably, so tiny a puncture was pro- 

 duced as to be barely visible except in a certain light to the unaided eye, and it 

 appeared moreover as if definitely sealed by the insect with some secretion 

 after oviposition. This may possibly be a very important part of its final 

 operations, as on several occasions I have found an exuberant fungus growth, 

 brown in colour, sprouting at little fissures accidently produced in tsetse pupae. 

 Later I hope to be able to study this further. 



I should perhaps add that the night when the Mutilla was working was 

 bitterly cold, a rather surprising fact, seeing that as a rule these insects are so 

 lethargic except on bright sunny days. 



I have now examined carefully all the pupae to which this female has access, 

 and 7 out of the 20 show this evidence of attack. There is therefore every 

 reason to believe that the Mutilla can be raised experimentally in some num- 

 bers and without any great difficulty in the laboratory. Their hardiness, their 

 activity in finding food for themselves, and their longevity make them singularly 

 easy to deal with, so that I expect shortly to be able to submit a further report 

 on the subject. 



In regard to their general habits, they do not as a rule become active till 

 the middle of the afternoon, remaining until then hidden beneath objects on 

 the top of the ground, or buried beneath the superficial layers of the soil. The 

 female is an adept at burrowing, and the male in pursuit of her does not hesi- 

 tate to force his way into the soft earth. Both sexes run with extreme 

 activity, the male being unusually loth to take to flight for a winged insect. 

 55287—28 2 



