86 HYMENOPTERA. 



the bees : there are many others, but enough has been ad- 

 duced to show the probability of our position. 



In the year 1851, \vhen on a collecting excursion to the 

 Isle of Wight, I captured Philantlnis triangidum in great 

 numbers in Sandown Bay, since which it has been taken in 

 the same situation by other Entomologists ; but I have 

 reason to fear this fine insect has now quitted that locality. 

 Mr. Pascoe, who resided at Ventnor some months during the 

 past season, searched diligently for the species without find- 

 ing a single specimen. Assuming this to be an example of 

 insect migration, what circumstances have occurred likely to 

 prove an adequate cause? The same slopes in which I found 

 them burrowing still remain at the foot of the clifis, the 

 blackberry bushes still blossom, on the flowers of which I 

 took them in plenty, and their prey, Halicti and Hive Bees, 

 are no doubt as plentiful as ever : such being the case, it 

 becomes a matter of impossibility even to suggest a probable 

 cause, since I am not aware of any attack on PJdlanthus by 

 any species of parasite likely to render their old locality un- 

 tenantable. xVtmospheric changes may no doubt operate 

 strongly upon them — a long continued season of cold wind 

 and rain, coming in an unfavourable direction, might so in« 

 terfere with their operations as to drive them to setk some 

 more sheltered situation ; but of all places in the Isle of 

 Wight, the Undercliff is, perhaps, the least likely to be so 

 visited. 



Among the captures made by Mr. Pascoe of Hymenop- 

 terous insects, in the above locality, I noticed examples of 

 most of the rarities which fell to my lot sixteen years ago, 

 the rarest being Aporms unicolor, and next in point of rarity 

 may be mentioned the male of 3Iethoca ichneumonides. I 

 have only taken five specimens of this male during the long 

 period of my Hymenopterous explorations. It is very pro- 



