HYMENOPTERA-BEES 165 



that this author, in summarizing previous observations, mentions 133 plants in which 

 perforation has been noticed. A. Schulz rightly remarks (' Beitrage/ II, p. 203, 

 note 3) that if the review is a full one this memoir cannot claim to be absolutely 

 exhaustive. 



Hermann Muller speaks as follows ('Alpenblumen,' pp. 521, 522) with regard to 

 the visits of parasitic humble-bees to flowers. From a high degree of adaptation 

 to flowers, which was necessary when they reared their own offspring, they have 

 lapsed into brood-parasitism, retaining only such adaptations as are requisite for 

 their own maintenance. In consequence they have certainly not become more 

 specialized in relation to flowers than their social ancestors, which collected the 

 food necessary for their communities. They possess, at most, some amount of 

 inherited skill which is displayed during their visits to flowers, though it is no 

 longer exercised for the benefit of a community. What then do we find here? 

 Anemophilous flowers, pollen flowers, and flowers with nectar completely exposed, 

 or only partially concealed yield far too httle food to be ever touched by these 

 parasitic humble-bees, which only have to provide for themselves, and are, therefore, 

 perfectly free to follow their own inclinations and consult their own convenience. 

 They never attempt to plunder lepidopterid flowers, for such endeavours are 

 exhausting and often fruitless even for humble-bees. The rich supplies of nectar 

 readily accessible to them in nectar flowers and social flowers with completely 

 concealed nectar {CS) constitute the only and never-failing goal of their activity, 

 and their proceedings are of an easy-going character that is quite unparalleled 

 among humble-bees collecting food for the benefit of a community. When we 

 consider that even bee flowers are visited by them but rarely, and that most of their 

 visits are paid to Composites and allied plants, which are easy to plunder and offer 

 a rich booty, we can scarcely avoid the conclusion that, since relinquishing the 

 task of rearing their own brood, they have become less skilled in plundering 

 speciaUzed bee flowers, or even if they fully retain this aptitude the easy parasitic 

 life prevents its full exercise. 



The eloquent account given by Hermann Muller led me (' Bliitenbesucher,' I, 

 p. 6; II, p. 10) to test the correctness of his views, and I reached the following 

 conclusion. Parasitic humble-bees chiefly visit brightly coloured social flowers 

 and next to these prefer flowers with concealed nectar, bee flowers, white and 

 yellow social flowers, and humble-bee flowers, while now and then they even visit 

 flowers with half-concealed nectar, but they avoid anemophilous flowers, pollen 

 flowers, flowers with exposed nectar, and lepidopterid flowers. 



The habit possessed by female humble-bees of chiefly seeking out hymenopterid 

 flowers, while the males give preference to social flowers, is exaggerated in the 

 parasitic genus Psithyrus, which constitutes a small side-branch of the group. The 

 species of this genus consequently prefer dark-coloured flowers even more than 

 do the short-tongued species of Bombus (Loew, ' Blumenbesuch,' I, p. 35). 



The suctorial apparatus of Anthophora, Eucera, Melecta, Megachile, Osmia, 

 Anthidium, Heriades, Chelostoma, Stelis, Coelioxys, and the remaining long-tongued 

 Apidae in general, corresponds with that of Apis, Bombus, and Psithyrus, especially 

 in the often marked elongation of the ligula and its sheath. 



The species of Anthophora, like humble-bees, greatly prefer the flowers of 



