July, 1901] 



PSYCHE. 



''2;i 



ful examination of the literature would 

 probably show that they have also been 

 taken in the nests of other species of 

 Formicidae in this country. Of their oc- 

 currence in the tropics, however, little is 

 known. Wasmann (loc. cit.) mentions 

 the larva of one species as occurring in 

 Madagascar with Canipo/ioli/s Hildc- 

 braiiiiti, and the larva and pupa of 

 another as having been found in ant 

 nests in Australia. He also records 

 the occurrence of these larvae in termite 

 nests in Madagascar and Porto Alegrc, 

 Southern Brazil. 



During the Christmas holidays, 

 while collecting ants at C'uernavaca, 

 Mexico, I happened on some Microdon 

 larvae in the nests of Pscudomyniia 

 gracilis Fabr. var. ntexicana Emery, one 

 of the numerous varieties of a tropical 

 ant which seems to be of rather common 

 occurrence from the extreme southwest 

 corner of Texas (about Brownsville 

 according to Townsend,*) to Rio 

 Grande do Sul in Southern lirazil (v. 

 Ihering.f) In one of the Pseudomyrma 

 nests which was in a hollow acacia limb 

 and contained a deillated queen, about 

 a dozen workers and a lot of larvae and 

 pupae, a mature Microdon larva was 

 found attached to the wall of the chamber 

 in the midst of the ants. The other 

 Pseudomyrma nest was in one of the 

 epiphytic Tillandsias.t This contained 



*0n the Biogeography of Mexico and the South Western 

 United States II. Trans. Tex. Acad. Sci, 1S97. Vol. II 

 No. I, p. 72. 



tDie Ameisen von Rio (irande do Sul. Berlin. Entomol. 

 Zeitschr. Bd. 39. Hett, 3 1894 p. 3S3. 



?For a description of these singular nests the reader may 

 be referred to my article on " Compound and Mixed Nests 

 of American .^nts," Am. Naturalist igoi. 



a Microdon puparium from which the Hy 

 had already escaped. The anterior 

 third of the pupa-case had been pushed 

 off in the manner characteristic of the 

 Cyclorhapha. 



The occurrence of such bulky and de- 

 fenceless Dipteron larvae in the nests of 

 large-eyed, active ants like the Pseu- 

 domyrnias, which are, moreover, pro- 

 vided with powerful stings, is nearly as 

 surprising as their occurrence in the nests 

 of Vespa. Apparently the relations be- 

 tween the larvae and their hosts are the 

 same as those of other species of Micro- 



-Adult larva of iNIiciodon sp., living in nests of /'-tf«(/f?- 

 iiiyrma gracilis Fabr. var ?«f,r/crt«rt F.m. X 5. 



don larvae to the less formidable ants 

 of Europe and the United States. Adlerz 

 (loc. cit.), who was able to make some 

 observations in Sweden, came to the 

 conclusion that the Microdon larvae sub- 

 sist on the moist and tender wood, form- 

 ing the walls of the ant galleries in pine 

 stumps although they were also found in 

 burrows in the dry bark. The ants 

 seemed not to pay the slightest atten- 

 tion to the Dipteron larvae living in their 

 midst. Wasmann § also found that the 



§ Erster Nachtrag zu den .Ajneisengaesten von Hollaen- 

 disch Limburg. Tlijdcshr. voor Entomol. Deel 49. 1898 p. 7. 



