106 THE DISTRIBUTION, RARITY 



There is a rare little bee (Macropis labiata) 

 which at one time was looked upon as an extreme 

 rarity, having only occurred three or four times 

 in this country. Mr. F. Enoch, comparatively 

 lately, took a fair number on the flowers of the 

 greater loose-strife (Lysimachia vulgaris) along 

 the canal at Woking ; now that its food-plant is 

 known, it has occurred in several other places in 

 numbers, and no doubt wherever the Lysimachia 

 is abundant Macropis will probably occur, 

 but how the little creature has been distributed 

 over the places where this plant occurs, which 

 are often far distant from each other, seems to 

 me to be an unsolved problem. Then there is 

 another puzzling point, and that is the extreme 

 rarity of certain insects. No doubt in many 

 cases this is due to ignorance of their habits, 

 as it has frequently happened that species 

 once considered of great rarity have occurred in 

 abundance when their habits have been dis- 

 covered, as in the case of Macropis, but there are 

 some cases which do not seem to be explainable 

 in this way. I will again give an example 

 which has been specially under my own obser- 

 vation. Dufourea vulgaris, a little black bee, 



