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 Miiller 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 little 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 
specialized bee flowers, or even if they fully retain this aptitude the easy parasitic 
life prevents its full exercise. 
The eloquent account given by Hermann Miller led me (‘ Bliitenbesucher,’ I, 
p- 6; II, p. ro) 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 
