19G Dr. T. A. Chapman on the Parasitism 



queen-grub must bear as a meal much the same rchition to a 

 Avorker-grub that the pabuhim ofiorcil by tlie wasps to a 

 Ii/i ijnjjhorusAaryix, on the sup])ositiou that it is a queen-grub 

 because it is in a queen-cell, does to that they would offer to 

 it in a worker-cell, where they must suppose it to be a worker- 



As to the difficulties which Mr. ^Murray finds in the Rhipi- 

 phonis beginning its repast at the head of its victim, he falls 

 again into the error of su})posing that Mr. Smith ])ostulates 

 that the larya of RJiijJijjhorus should perambulate in search of 

 pabulum : this, however, only explains a part of his difficulty, 

 as Mr. Stone's observations and the requirements of the theory 

 that I accept from ]\Ir. Denison show that the IiIiij>ij)hon(s- 

 gYuh really does begin his attack at or near the head. Here 

 I cannot help suggesting, in ])arcnthcsis, somewhat mis- 

 chievously perhaps, for Mr. Smith's consideration, that if the 

 Qgg lies domiaut during the feeding of the wasp-grub, it must 

 remain so at the bottom of the cell; and then, of course, to the 

 confusion of all parties, the attack of Rhipijyhorus would 

 " begin at the tail." 



]Mr. Murray clearly believes that he has here made a strong 

 point. He assumes, with a])parcntly logical accuracy, that 

 if the Rlrq^ipliorus begins to devour its victim at the head, it 

 necessarily last eats the tail, and must thus, when it has com- 

 pleted its meal, have its head where its victim's tail was. 

 Part of this en*or arises, as I have said above, from the sup- 

 position that the larva crawls about above the cells in search 

 of a victim — a supposition that no one will object to my dis- 

 missing as untrue. But were it true, it avouIci not alter my 

 position that the wasp-grub can be easily (and is) attacked 

 first near its head, yet the parasite assume the proper position 

 in the cell. Let it be clearly imderstood that the wasp-larva 

 is not to be eaten downwards, segment by segment, as though 

 it Avere a can*ot. It is doubtless eaten just as the larva of 

 Odynerus spinipes is by that of Clirysis hidentata, viz. its 

 juices sucked out, at Jirst partially, of course, leaving it flaccid, 

 so that both larvte might easily be arranged side by side in 

 the cell, the tail sucker of the victim now probably relaxing 

 its hold of the cell-wall ; afterwards more thoroughly; and, if 

 the parallel holds good, the victim is reduced to very small 

 dimensions indeed before any thing like eating takes ])lace. I 

 have often seen a larva of Odynerus sjyiriipes reduced to very 

 small bulk without any trace of even a microscopic opening 

 in the skin being discoverable. In this way there is no diffi- 

 culty in understanding how the Blnpiphorus-larvei is found, 

 when full-fed, with its head to the mouth of the cell. It 



