SPHEGIDAE BEMBECIDES I 2 I 



of other burrows.' In the course of twenty-four hours the 

 egg hatches, and the larva in two or three days completely 

 devours the stock provided for it. The mother - wasp then 

 returns with another fly — this time probably a larger one — 

 penetrates rapidly to the bottom of the burrow, and again re- 

 treats, leaving the second stock of provisiojis for the benefit of 

 the greedy larva. These visits of supply are repeated with increased 

 frequency, as the appetite of the larva for the benefit of which 

 they are made increases with its growth. During the fourteen 

 or fifteen days that form this portion of the life-cycle, the single 

 larva is supplied with no less than fifty to eighty flies for food. 

 To furnish this quantum, numerous visits are made to each 

 burrow, and as the mother Bemhex has several burrows — though 

 how many does not appear to be known — her industry at this 

 time must be very great. All the while, too, a great danger has 

 to be avoided, for there is an enemy that sees in the booty 

 brought by the Bemhex to its young, a rich store for its own 

 progeny. This enemy is a feeble, two-winged fly of the family 

 Tachinidae and the genus Miltogramma ; it hangs about the 

 neighbourhood of the nests, and sooner or later finds its 

 opportunity of descending on the prey the Bemhex is carrying, 

 choosing for its purpose a moment when the Bemhex makes a 

 brief delay just at the mouth ■ of the burrow ; then down comes 

 the 2rdtogramma and lays one, two, or three eggs on some portion 

 of the booty that may be projecting from beneath the body of 

 the wasp. This latter carries in the food for its own young, but 

 thus introduces to the latter the source of its destruction, for the 

 Miltogramma larvae eat up the supply of food intended for the 

 Bemhex larvae, and if there be not enough of this provender they 

 satisfy their voracity by eating the Bemhex larva itself. It is a 

 remarkable fact that notwithstanding the presence of these 

 strange larvae in the nest the mother Bemhex continues to bring 

 food at proper intervals, and, what is stranger still, makes no 

 effort to rid the nest of the intruders : returning to the burrow 

 with a supply of food she finds therein not only her legitimate 

 offspring, a single tenant, but several others, strangers, it may 

 be to the number of twelve ; although she would have no 

 difficulty in freeing the nest from this band of little brigands, 

 she makes no attempt to do so, but continues to bring the 



^ See on this point the note on p. 130. 



