1924 ] 
Flower Visits of Insects II 
99 
efficient pollinators and often are so small that they can get the 
nectar without much probability of touching the anthers and 
stigmas. 
Diptera. — Of 3775 visits of 403 species to 266 flowers, 48 
per cent are to Mis, 25.4 to Pol, 59.3 to white, 32.9 to yellow, 
21.8 to Umbelliferse and 28.2 to Compositse. Mis shows 31.9 
per cent of the flowers, Pol 8 . 6 and white 46.9. One prefers Ma, 
six prefer Mi, 21 Mas, 158 Pol, 192 Mis, 9 red, 133 yellow, 253 
white. Visits to red are 7.7, Alps 22.2, Low Germany 24.2, 
Berlin Garden 33.1. After June the maximum changes from 
A 35.4 to B’ 48.1. Yellow changes from 37.7 to 28.3. Of 256 
non-pollinating visits, 32 . 8 are to Ma, 21.0 to Mas, 17.0 to Pol 
and 38.6 to red. 
Next to bees, flies visit more species of flowers and make 
more visits than any other anthophilous insects. Being 31.2 
per cent of the species, they make 27 per cent of the visits, 36.8 
per cent of the total visits to Pol. The total number of flowers 
visited is less than that for Bombidse or Halictidse. The flowers 
visited by 62 or more flies are Solidago canadensis 62, Zizia 
aurea 63, Siam cicutcefolium 71, Cicuta maculata 82, Pastinaca 
sativa 113, Heracleum lanatum 121, Aster ericoides villosus 121. 
The flowers showing the greatest number of siphonate flies are 
Solidago canadensis 16, Boltonia asteroides 18, Bidens aristosa 
21, Pycnanthemum flexuosum 22, Eryngium yuccifolium 23 and 
Aster ericoides villosus 31. 
The importance of flies as pollinators is greatly exaggerated. 
They are apt to show as the exclusive visitors in unfavorable 
weather, or in localities where the flora and insect fauna have 
been greatly disturbed. The proboscis is usually rather thick 
so that the pollen readily touches and adheres to it, but the more 
highly specialized for probing flowers it becomes, the less likely 
it is to extract the pollen. In the lists have been admitted flies 
which should probably be excluded on account of their small 
size, or ability to extract nectar or eat pollen without effecting 
pollination. 
