340 ENTOMOLOGICAL NEWS. [Dec, '04 



Grav. ; for Formica fusca L,. and Atenieles emarginaius Payk., 

 etc., etc. 



Now this array of facts was gathered in Europe, but it led 

 the famous biologist to surmise that probably a similar relation 

 existed between the American Xenodusa cava Lee. and its hosts, 

 namely : Camponotus pennsylvaiiiais Deg. , Caniponotus ligni- 

 perd^is var. pictus For., Formica sa7iguinea subsp. rubiciinda 

 Em., Formica pallidefulva , subsp. schatifussi Mayr., * and 

 Formica exsectoides For. 



However, no pseudogynes had as yet been observed in any 

 of the colonies of the ants just mentioned. 



Wasmann, therefore, repeatedly called my attention to this, 

 and in his letter of March 19, 1901, directed me to attend 

 especially to the following points : (i) Which is the host that 

 rears the larvae of Xenodusa cava f and (2) Do the colonies of 

 that host contain pseudogynes ? 



On August 23, 1900, I had been so fortunate as to find near 

 Prairie du Chien, Wis., seven specimens of Xenodusa cava 

 (Fig. i) in a nest of Camponotus pictus. Subsequently I exam- 

 ined and searched not only the nest of C. pictjis, but all the 

 nests in the neighborhood with the hope of discovering, if 

 possible, the larvae of Xefiodusa cava and the supposed pseudo- 

 gynes. The task was tedious and discouraging. The soil 

 which the ants had chosen for their subterranean habitation 

 was rather ston)^ ; besides, the time when the Xenodusse were 

 found was precisely the period in which some ant-guests 

 change their hosts, so that it was altogether doubtful whether 

 the specimens sought for would be contained in the nest of 

 Campo7ioius picttis. In fact, it was not before the October of 

 1901, after many expeditions during the entire spring and 

 summer seasons, that my efforts were crowned with success. 

 In a colony of F. rubicunda within some 100 feet of the place 

 where Xenodusa cava was originally observed, a number of 

 true pseudogynes were discovered. They are shown in the 

 accompanying photograph' ( Fig. 2). Great was my joy when 

 beholding for the first time these helpless creatures with their 

 small abdomen and strongly developed mesonotum. Their 

 whole behaviour excellently corresponded to the descriptions I 

 had read in the writings of Wasmann, and their strange thorax 

 in particular closely resembled that of the pseudogynes of 

 Formica sangiiinea received from Holland. This is, to my 

 knowledge, the first case observed in this country of pseudo- 

 gynes found in the district of Xenodusa cava. 



Now from analogy, it was a priori probable, that the same 



*This fact I owe to Professor Wheeler, who wrote in his letter of 

 September 8, 1902, that he had found Xenodusa cava in nests of 

 F. schaufussi and C. piclus on several occasions. 



