THE CANADIAN ENTOMOLOGIST. 



NOTES ON THE MOUTH-PARTS OF BOMB-US. 



BY T. D. A. COCKERELL AND JOHN M'NARY, E. LAS VEGAS, N. M. 



We have lately studied the mouth-parts of a number of species of 

 Bombus, both American and European, and adding our results to those 

 obtained by Radoszkowski (1877) we find as follows :— 



(1) Taking the first joint of the labial palpus of the 9 as an index 

 of the length of the mouth-parts (it is especially convenient for accurate 

 measurement), we find that the longest mouthed species is B. Gerstackeri, 

 from the European Alps (our examples were collected by Friese at 

 Engelberg), a species known to be the exclusive visitor of Aconitum 

 lycoctonum in that region. The Aconitum (Knuth, Bliitenbiologie, Vol. II., 

 p. 53, fig. 20) has the hood enormously produced, and is adapted only to 

 bees with extremely long tongues. 



(2) No Rocky Mountain or other American Bombus examined by us 

 has nearly such long palpi (or tongue) as B. Gerstackeri, nor have we such 

 an Aconite as A. lycoctonum. Our longest-tongued type seems to be B. 

 Nevadensis, which visits Delphinium. 



(3) The species with shortest mouths are mostly high-alpine or arctic: 

 proximus, melanopygus, lapponicus, viduus. B. terrestris also ranks with 

 these as one of the shortest-mouthed ; it is remarkable that the species 

 which superficially looks exactly like B. terrestris, namely, B. liortorum, 

 is one of the longest-mouthed of all, having the first joint of labial palpus 

 about 6y 2 mm. long. We have both terrestris and hortorum from Inns- 

 bruck, collected by Friese. 



(4) B. ligusticus, ruderatus and ussurensis rank with the longest- 

 mouthed species, and probably, like Gerstackeri and hortorum, are adapted 

 to Aconitum. 



(5) The commonest length for the first joint of the labial palpi is from 

 4 to 4*^ mm. Here come B. juxtus, Morrisoni, rajellus, muscorum 

 senilis, fragrans, equestris, sylvarum, Stewenii, Latreillelus, Mlocosewiczi, 

 calidus. The American virginicus and Kincaidii fall short of this by a 

 small amount, although they are large bees. 



(6) The second joint of the labial palpi does not usually enlarge in 

 proportion to the first, hence the longest-mouthed species have the great- 

 est difference between the joints. In such species as ruderatus, ussur- 

 ensis, etc., the first joint is from 5)3 to 6 times as long as the second. In 

 nearly half the species, the first joint is from 4 to 4^ times as long as the 

 second ; in proximus it is only 2^ to 3 times as long. In Gerstackeri the 



