AMMOPUILA AND HER CATERPILLARS. 9 



were under ground in the day-time. The species observed by 

 Eabre knew, by some subtle instinct, where to find the worm,, 

 and unearthed it from its burrow. Urnaria, on the contrary, 

 never dug for her prey, but hunted on bare ground, on the- 

 purslane, and most of all on the bean-plants. These were ex- 

 amined carefully, the wasp going up and down the stems and 

 looking under every leaf, but the search was so frequently un- 

 successful that in estimating their work we are inclined to think 

 that they can scarcely average one caterpillar a day. When 

 they were hunting over bare ground they often paused and 

 seemed to listen, and in the beginning we expected to see them 

 burrow down and drag a victim from under the soil, but this 

 never happened. 



In this species, as in every one that we have studied, we have 

 found a most interesting variation among the different individu- 

 als, not only in methods but in character and intellect. While 

 one was beguiled from her hunting by every sorrel blossom she 

 passed, another stuck to her work with indefatigable persever- 

 ance. While one stung her caterpillar so carelessly and made 

 her nest in so shiftless a way that her young could only survive 

 through some lucky chance, another devoted herself to these 

 duties not only with conscientious thoroughness but with an ap- 

 parent craving after artistic perfection that was touching to see. 



The method employed by the Ammophilae in stinging their 

 prey is more complex than that of any other predatory wasp. 

 The larvse with which they provision their nests are made up 

 of thirteen segments and each of these has its own nervous 

 center or ganglion. Hence if the caterpillar is t-o be reduced to 

 a state of immobility, or to a state so nearly approaching im- 

 mobility that the egg may be safely laid upon it, a single sting, 

 such as is given by some of the Pompilidae to their captured 

 spiders, will be scarcely sufficient. All this we knew from Fa- 

 bre's "Souvenirs," and yet we were not at all prepared to believe 

 that any plain American wasp could supply us with such a 

 thrilling performance as that of the Gallic hirsuta, which he 

 so dramatically describes. We were, however, most anxious 



