TAPERS OX ZOOLOGY 159 



the smallest number of species. Many western states, with 

 their diverse geolojiical featiires, have listed nearly 

 tweutY-fiye species of this family, and I believe the lists 

 will be considerably increased in the future. Florida is 

 accredited with only four sj^ecies, and all of the Gulf 

 states appear to have a paucity of species. The writer has 

 increased the Ilinois list from ten to fifteen species of 

 Bremklac, and believes the list will in time be swelled to 

 twenty species. 



Illinois has representatives of eight of the ten groups of 

 Bremidar erected by Dr. Franklin and Radoszkowski. Five 

 of the species of BreniKS (tcrricoJa, frigidus^ nevadensis, 

 horealis, and per plexus) considered in these keys are here 

 listed for Illinois for the first time. B. frigidus is included 

 in the list because of the presence in the Illinois Xatural 

 History Survey Collection of specimens of this species 

 collected in Xorthern Illinois by Mr. O. S. Westcott. 

 B. pcrplcius is likewise reported from Xorthern Ilinois by 

 Mr. Westcott. B. affinis, teniarius^ rufocinctiis^ Ps. insu- 

 larius and ashtoni have not as yet been taken in this state, 

 but will probably be captured eventually in the northern 

 part of the state. The Illinois species of bumblebees range 

 from Lower Austral to Boreal forms. The majority of the 

 species are principally forms that reach their greatest 

 abundance in the Transition and Upper Austral Zones. 



The distribution of the species of Psithyrus depend upon 

 the distribution of the species of Brcmiis whose nests they 

 infest. In Illinois I have shown that Ps. variabilis infests 

 the nests of B. pcnnsi/lronieus (1916). Ps. variahilis is 

 therefore to be expected wherever B. pcnnsijlvanicus 

 occurs, other conditions being the same. It is not known 

 in this country whether the same species of PsitJii/rus is an 

 inquiline in nests of more than one species of Brenius or 

 not. Sladen (1915) found Ps. insularis in the nest of B. 

 ffavifrons. Ps. insularis is, however, listed from regions 

 B. farifrons is not known and is not even likely to occur; 

 indicating that Ps. insularis must be an inquiline in the 

 nest of more than one species of Bremus. The distribution 

 of Ps. lahoriosus in this and other states has impressed 

 the writer with the belief that it is an inquiline in the nests 

 of B. fervidus or B. vaga ns. 



