16,-1 Bulletin Wisconsin Natural History Society. [Vol. 8, No. 4. 



the tongue reaches a length of 19-21 mm. Undoubtedly this spe- 

 cies would be able to produce the desired results if present in suf- 

 ficient numbers, but being in the minority (as the letter from the 

 New Zealand government indicates) its influence is noticeable to 

 a slight degree only. 



At Milwaukee the following bees have been seen on the flowers 

 of the red clover: Apis mellifcra L. (honey bee), Osmia atriven- 

 tns Cr., Megachile zvootoni Ckll., Synhalonia atriventris Sm., 

 Bombus virginicus Oliv., B. americanorum Fabr., and B. pennsyl- 

 ■vanicus DeG. (fervidus). Of the three bumblebees B. america- 

 norum and B. pennsylvanicus are more frequent visitors than B. 

 virginicus.. At Carlinville, Macoupin Co., in southern Illinois 

 Robertson 6 took among other visitors of the red clover five bum- 

 blebees : B. americanorum Fabr., B. pennsylvanicus DeG., B. rid- 

 ingsii Cr., B. separatus Cr., and B. vagans Sm. 



On account of the tube-length of the flower no bumblebee with 

 a tongue-length under 9 mm. can be regarded as a reliable polli- 

 nator, as has been shown above. A measurement of the mouth- 

 parts* of eleven species of bumblebees from the Milwaukee region 

 has furnished the following figures : 



Bombus americanorum Fabr. about 14 mm. 



" pennsylvanicus DeG. about 14 mm. 



" auricomus Rob. about 12 mm. 



" ridingsii Cr. about 10 mm. 



" separatus Cr. about 8 mm. 



" virginicus Oliv. about 8 mm. 



" consimilis Cr. about 7 mm. 



" hiuitii Greene (tenarius) about 7 mm. 



" juwtus Cr. about 7 mm. 



" terricola Kirby about 6 mm. 



" affinis Cr. about 5 mm. 



According to these figures only the four species at the head 

 of the list would fulfill the requirements. Of these B. auricomus 

 and B. ridingsii are, in our region at least, not so common as B. 

 americanorum and B. pennsyh'anicus, the last named being espe- 



6) Chas. Robertson, Flowers and Insects, VIII; Bot. Gaz., Vol. 

 XVII (1892), p. 177. 



•') In comparing the mouthparts of a number of American and 

 European bumblebees, Cockerell and M'Nary have taken the length of 

 the first joint of the labial palpus as an index. (Canad. Ent., Vol. 

 Vol. XXXIV, pp. 71-72). 



