1907.] Wheeler, The PolymorpJmm of A^Us. 43 



pseudogyne of a variety of C. se7^ex Fabr. from Bolivia/ and Miss Holliday ^ 

 has called attention to a couple of pseudogjues of C. maculatus vicinus 

 Mayr. var. nitidiventris Emery collected by Professor Harold Heath at San 

 Jose, California. Very recently Emery has discovered a pseudogyne of C. 

 igneus (?) in the Baltic amber.^ In another place* he has described what he 

 regards as a pseudogyne of a Myrmicine ant, Pheidologeton diversus, of 

 India. I figure some specimens of two different varieties of Myrmica rubra 

 (sidcinodoides and schencki) which have a thoracic structure that may pro- 

 perly be called pseudogynic (PI. IV, Figs. 45 and 46, 48 and 49) when 

 compared with that of the normal worker (Fig. 47). The mesonotum is 

 distinct and unusually convex, and there are clear traces of scutellar and 

 metanotal sclerites. Some specimens (Fig. 45) bear vestiges of wings like 

 those of the pterergates. As there is little probability that such forms are 

 due to Lomechusini, it has been suggested that other parasites may be re- 

 sponsible for their production. I am inclined to believe that they arise 

 occasionally even in uninfested colonies. If it be true that these anomalies 

 as well as the above described pseudogynes of Formica arise from neglected 

 immature female larvae, it should be possible to produce them artificially 

 by separating such larvte from their nurses for several days. During the 

 coming summer I hope to take vip some experiments with this end in view. 



4. The Commensalism of Metopina. 



The parasitic insects considered in the preceding sections of this article 

 are of more than usual interest because they produce certain effects notice- 

 able both in the structure and behavior of their Formicid hosts. While all 

 these effects are Avrought through a withdrawal of nourishment from the 

 developing larvae, each natural group of parasites adopts a different method. 

 Thus the ectoparasitic Orasema larva extracts important juices from the 

 body of the Pheidole larva directly and with great rapidity, thereby reducing 

 its host to a mere skin, which, though still able to pass on to the ])upal stage, 

 no longer possesses sufficient substance or vitality to reach the imaginal 

 stage. The Mermis larva develops much more slowly within the alimentary 

 tract of the ant larva and appropriates a portion of the food before it has 

 been metabolized and converted into living comj^ounds of high morpho- 

 genic potential. Finally, the presence of the Lomechusini within the Formica 



' Iiitorno al Torace delle Formidie. Bol!. Soc. Ent. Ital.. XXXII, 1900, p. 17 (of extract), 

 fig. 14. 



^ Some ErgatOKynic Ants, loc. cit., pp. 313-315, f\e. K. 



3 Deux Fouriiiis de I'Ambre de la Haltique. Bull. Soc. Eiit. France, Anii^e 1905, No. 13, 

 .p. 189, fiff. 2. 



■' Zur Keiuitniss de.s Polymorplii.snius, loc. cit., p. 605-608, figs. 



