ENTOMOLOGICAL SOCIETY OF ONTARIO. 119 



THE INTERRELATION OF INSECTS AND FLOWERS. 



During the latt 8 years there have appeared from the pen of Mr. Charles Robertson, 

 of Carlinville, 111., several most interesting articles on the inter-relation of insects and 

 flowers. The titles are as follows : 



Botanical Ga:.ette — 



1886. Notes the on pollination of Asclepias. 



1887. Insect relations of certain Asclepiads. 



1887. Fertilization of Calopogon parvillorus. 



1888. Effect of the wind on bees and fiowers. 



1888. Zygomorphy and its causes . I-III. 

 1889-93. Flowers and Insects : I-X 1. . 



Trans. Am. Eat. Sue. — 



1889. Synopsis of North American species of Oxybelus. 

 1891-93. Descriptions of new species of North American Bees. 



Trans. St. Lota's Acad, of Science — 



1891-92. Flowers and Insects : Asclepiaddcen' to Sctofulariicr ;e, rnibellifer;o, Labi - 

 at;*". 



Mr. Robertson began in 18SG to study the visits of insects to ilowers and by his per- 

 severing observations he has succeeded in collecting an enormous number of facts which 

 he has published mostly in the Botanical Gazette and in the Transactions of the St. Louis 

 Academy of Science. 



He has studied the subject especially from a botanical point of view and has given 

 particular attention to the attractions offered to insects by the flowers of different species 

 of plants, to the peculiarities of arrangement of their different parts, to their coloration,, 

 and to the modifications which many flowers seem to have undergone from their being 

 constantly frequented by certain species of insects. 



Such studies have nevertheless an immediate bearing on entomology, as they give us 

 at the same time an insight into the purposes of insects in visiting flowers, into their 

 habits of feeding and collecting either nectar or pollen, or both at once, and into the in- 

 telligence they display in order to attain their tnd. The close attention thus necessarily 

 given to insects, has had besides the natural result of causing Mr. Robertson to discover 

 that many of those insects which he was observing in his locality, Carlinville, 111., had not 

 even been described. Therefore, he found it necessary at first to pay particular attention to 

 collecting and determining insects. He was helped in this work by specialists in Diptera 

 and Coleoptera, and had himself to work out and describe many species of Hymenoptera r 

 10 out of 14 species of Oxybelus, 28 out of 30 of Andrena and at least thirty other species 

 of Andrenidse. The descriptions of these have appeared in the Trans. Am. Ent. Soc. 

 18891893. 



The two groat agencies of cross-fertilization of flowers are the wind and insects ; 

 hence Mr. Robertson has thus been led to notice some intere.sting facts concerning the 

 effect of wind on bees and flowers. — Bot. Gaz, xiii , 1888, p. 33. 



The first papers by Mr. Robertson are on the pollination of Ascelepias, the flowers 

 of which are most interesting in their peculiar adaptation for cross-fertilization by the 

 agency of insects. Their structure and the great difficulty the smaller insects have in 

 effecting pollinations, leads Mr. Robertson to believe, "that bumblebees have had most 

 influence in modifying the flowers, and they are the most common visitors after the hive 

 bees. Hive bees, it is to be remembered, do not belong to our fauna." ' 



Our space is too limited to allow us to follow the writer into what he has observed 

 in all the different orders and speci(s of flowering plants studied ; but the names of all 

 the insects observed visiting the flowers, are given, as well as tabular data of the les- 

 ppctive number of visitors of the different classes, Hymenoptera, Diptera, Lepidoptera,- 



