.-IXTS. 



rado. Brues ( 1903/7 ) has described an extraordinary, lemon-yellow 

 and very convex Microdon larva taken by Professor II. Heath from a 

 not of Mti<ii<-inin iniiiiiiuiin in California, and I have described a 

 very flat larva from the nest of Pseudoinynna inc.vicana ( 19016 ), so that 

 the larva? of at least four North American species are known. As 

 Lea ( 1893 ) has described a species (.17. -.'aricgatus ) from Australia, the 

 genus is probably cosmopolitan. The ants, as a rule, do not seem to 

 notice the Microdon larvae and pupae and these are left behind when the 

 ants move to a new nest. The young larvae seem to shrivel and die 

 when removed from the ants, but I have been unable to ascertain 

 what they find to eat in the nests. In one of my artificial formicaries 

 the ants killed a young larva that had failed to get hold of a surface 

 with its vulnerable creeping-sole. They turned the helpless creature 

 over on its back and for two clays kept licking and biting it till it was 

 reduced to a mere granule. According to Wasmann the fly, which is 

 more or less tomentose, is sometimes licked by the ants, but it seems 

 to spend little time in the nest. In my artificial nests the imaginal .17. 

 tristis on emerging from their puparia were attacked and killed by their 

 host, F. sclwnfitssi (Wheeler, 19080? ). 



(b) Mimetic, Loricate and SyinpJiiloiil Syncckctcs. These are the 

 most numerous and typical of the tolerated guests and appear to attain 

 their highest development among the Doryline ants. This is surprising 

 because these ants have no fixed abode and their synceketes have to 

 lead the life of camp-followers, moving from place to place in the 

 caravans of their restless hosts. This life has its compensations, how- 

 ever, for the Dorylines are powerful marauders and there is always an 

 abundance of fresh food to be had in their temporary quarters. For 

 nearly all that is known of these Doryline guests we are indebted to 

 Wasmann, who has shown in a long series of papers (1890-1904) that 

 they are mostly Staphylinid beetles and that among these the mimetic, 

 loricate and symphiloid types have been remarkably developed and inde- 

 pendently of one another in each hemisphere. Thus among the guests 

 of Dorylits and JEnictns of the Ethiopian region we have the mimetic 

 genera Dorylostcthus (Fig. 228, O, Dor\lobins, Dorylophila, Dorylo- 

 pora, Dorylocenis, Doryloiniunis, Dorylogastcr and Stilicus: the lori- 

 cate genera Pygostenus, Dor\lo.\~enus, Anomwiatophilus, Anoinma- 

 to.renus, Disco.renus, Minwcctc and Trilobitidius (the last a Silphid) ; 

 and the symphiloid genus Sympolcmon. Roughly corresponding to 

 these we have as guests among the Ecitons of tropical America the 

 mimetic genera Mimeciton (Fig. 228, A), Ecitophya, Ecitophila, Ecito- 

 uiorpha (Fig. 228, B). Ecitonilla, Ecito.renia, Ecitochara, Ecitopora, 

 Ecitotouia, Edtonusa; the loricate genera Xenocephalus, Ccphalo- 



