PERSECUTED AND TOLERATED GUESTS. 



in the same manner as Myrmedonia, for, when an ant tries to seize it, 

 it raises the tip of its flexible abdomen and seems to emit a whitish fluid 

 which causes the ant to start back, as if a flask of ammonia had been 

 suddenly uncorked in its face, thus giving the beetle time to run away. 

 Megastilicus is certainly too feeble to kill living F. e.vsectoides workers. 

 It probably feeds on the remains of insects brought into the nest or on 

 the larvae of the ants. 



The Synoeketes. For convenience in handling this large and heter- 

 ogeneous group I shall divide it into four sections : the neutral synce- 

 ketes ; the mimetic, loricate and symphiloid forms ; the myrmecocleptics, 

 and the strigilators. 



(a) Neutral Synoeketes. To this section may be assigned a number 

 of insects which pay no attention to the ants or their brood, but live 

 on the refuse or nest materials and spend their time seeking these on 

 the walls of the galleries and chambers. They do not mimic the ants, 

 although they are sometimes protected either by 

 small size, tough integument or by specially con- 

 structed cases. They seem to pass unnoticed by 

 the ants, or, if perceived, probably appear as a part 

 of the lifeless environment. Typical examples of 

 these neutral synoeketes are the tiny white Podu- 

 rans of the genus Cyphodeira [Beckia], so abun- 

 dant in the nests of many different ants, both in 

 Europe and America. They flit about the dark 

 galleries like diminutive ghosts and are probably 

 invisible to the ants. The slow-moving, snow- 

 white slater, Platyarthrus hoffmannseggi of 

 Europe, is similarly panmyrmecophilous and 

 elicits no more attention than the much smaller Cyphodeira. A whole 

 fauna of Trichopterygid beetles (Ptcnidinin, Ptilium, etc.), mites 

 (Lcclaps], Ceratopogon larvae, microlepidopteran caterpillars (Myrmc- 

 cocccla ochroceella in Europe and Epizeuxis americalis in the United 

 States ) and Phoridae may often be found in the superficial chambers 

 of ant-nests and undoubtedly obtain most of their food as scavengers 

 on the kitchen middens. Some of these creatures, like the Phoridae 

 with subapterous females (Commoptera solenopsidis, Xanionotiun hys- 

 trix, Ecitomyia zvheeleri] described by Brues. (1901, 1902^) from the 

 nests of various Texan ants, are of unusual interest on account of their 

 aberrant structure and relationship to the remarkable Termitoxenia 

 and Termitomyia of termite nests. 



Besides these insects, nearly all of which are of small size, one occa- 

 sionally finds certain larger larval and pupal forms which, one would 



FIG. 227. Larva 

 of Microdon tristis. 

 (Original.) 



