592 TRANS. ST. LOUIS ACAD. SCIENCE. 



Lepidoptera. ■ Rhopalocera., (lo) Papilio philenor L. ; (ii) P. as— 

 terias F. ; (12) Pamphila zabulon Bd.-Lec. 



Diptera. — Bombylid(K^ (13) Bombj'lius atricep's Lw. — all s. 



Gratiola Virginiana'L.. — The plants grow in thin patches 

 in wet places, and rise about a span high. The flowers are white 

 with the tubes greenish-yellow, the upper wall being densely 

 bearded with yellow hairs. The tubes measure about S mm. and 

 are strongly curved upward, so that the bee must turn with its- 

 ventral surface toward the anthers in order that its body may fit 

 the tube. Then the dense beard on the upper wall also opposes 

 a bee trying to enter right-side up. But the flower is so nearly 

 erect, and the tube is so strongly curved, that the large upper lip- 

 stands almost horizontally, forming a most convenient landing- 

 place. Consequently, it is easier for the bee to enter back down- 

 wards than in any other way. 



While, therefore, the flower has the appearance of a nototribe 

 flower, and no doubt w^as originally of that kind, the form of the 

 tube has been changed so as to make the flower sternotribe by 

 requiring the bee to reverse. Delpino has observed the same 

 thing in G. officinalis. The curvature of the tube also has the 

 effect of excluding unbidden guests of long tongues. 



I think the flower is specially adapted to small bees of the ge- 

 nus Halicttis, which are of the right size to enter the tube. In 

 Illinois in June, and in Florida in March, I have found it visited 

 abundantly, both for honey and pollen, by H. confiisus Sm. 5. 

 This bee crawls so far into the tube that it is entirely hidden 

 from view. 



The anthers and stigma are so closely approximated, that, in 

 the absence of insects, it seems as if self-pollination may readily 

 occur. 



Veronica Virginica L.* — The white flowers are crowded in 

 close spikes at the summit of the stalks, and are fertilized by in- 

 sects crawling over them. They appear to be male at first, the 

 anthers standing 7 mm. beyond the mouth of the tube, and be- 

 coming widely separated; in the female stage. The corolla tubes 

 measure 5 mm., and the nectar is sought by mid-length and long, 

 tongues. 



* On the genus, see Miiller, " Fertilization of Flowers," 43S & 634. 



