October, 'OS] JOURNAL OF economic entomology 283 



just beeu left and which it I'ecognizes from all the others. It touches it with 

 its palpi, makes an attempt, which does not seem to be entirely successful, to 

 insert its ovipositor, and once more licks the wound. Then there is another 

 and short walk in the vicinity, followed by a new visit to the same egg. This 

 time the Tetrastichus inserts its ovipositor at exactly the same point that it 

 did the two preceding times, holding it inserted about a minute. Then it is 

 withdrawn, and the parasite licks the wound again in a very lively way. 

 After this, without other interruptions than those of preliminary feeling and 

 that of consecutive licking, it thrusts its ovipositor twenty times in succession 

 into the egg. If we add the three preceding times, we reach the result that 

 during the forty-five minutes that the observation lasted, the parasite thrust 

 its ovipositor twenty-three times into the same egg of the beetle. All of the 

 insertions wei*e not identical, and the later ones, in a general way, were much 

 more rapid than the earlier ones. About the middle of the series they lasted 

 from a third of a minute to a half a minute; towards the end the insect took 

 time only to insert the piercer and to withdraw it. The method, however, 

 was the same in all cases, and always was accompanied l)y the preliminary 

 feeling about and the licking of the place. 



"The next day the egg which had been stung by the Tetrastichus was exam- 

 ined. It presented, near each other, four minute brownish spots, corre- 

 sponding to the wounds made by the ovipositor. The insect, in order to avoid 

 unnecessary trouble in searching again for the wound which it had previously 

 made, occasionally made a new perforation when it could not find the old 

 opening quickly enough. 



"What can be the reason for this singular manoeuver of the Tetrastichus? 

 It is evident that the insect finds in the egg of the Galerucella a food which 

 it likes, and that, using its ovipositor in another way than that which is 

 habitually done with these Hymenoptera, it employs it as we use a pin to 

 pierce the shell of an egg in order to suck its contents. If the wound which 

 has just been made is too small to be found readily, it can be noticed that the 

 place licked by the parasite is moist with the liquid which comes from the 

 interior of the egg; oftsn a real drop appears at the surface of the egg and 

 is rapidly sucked up by the parasite. 



"It cannot be doubted that one of the motives of the insect in giving its 

 blows with the ovipositor is from its individual interest, but it is not less 

 certain, on the other hand, as the fact even of its parasitism proves, that the 

 Tetrastichus, conformably to the instinct of other Chalcididse, uses its ovi- 

 positor to introduce its egg into the egg of the beetle. It seems that among 

 all of the thrusts of the ovipositor which it gives, there can be only a 

 small number intended for egg-laying. In opening the eggs of the egg groups 

 most visited by the Tetrastichus I have discovered only a very limited number 

 of eggs belonging to the parasite; but its ovoid, slightly incurved egg, about 

 .023 mm. long, is relatively easy to discover, and it seems very certain that 

 the number of eggs deposited is very far from being equal to the number of 

 thrusts of the ovipositor. One can even suggest, in a general way, that the 

 parasite does not place more than one egg in the egg of the beetle. On the 

 other hand, one can open the egg of a beetle which has received a number of 

 thrusts of the ovipositor without finding in its interior a single egg of the 

 parasite.^ And it seems to be a fact tbat in certain cases the Tetrastichus 

 pierces the egg of the Galerucella exclusively to nourish itself. 



'This was the case with the egg whicli has just heen uiemionefl. 



