44 Bulletin American Museum of Natural History. [Vol. XXIII, 



nest leads to a withholding of the necessary food from the larva^, or, if Was- 

 mann's view be adopted, at least to a withholding of the proper kind of food. 



All of the above insects are ravenous parasites which ultimately destroy 

 their hosts either individually or as communities. The insect to be de- 

 scribed in the following paragraphs is much more benign, for if it surrep- 

 titiously appropriates some of the food that has been given to the larval 

 ant, the amount it consumes seems to cause no serious inconvenience to its 

 host. It is conceivable, however, that the presence of this commensal in 

 great numbers might lead to very appreciable disturbances in the trophic 

 status of a colony. The insect is a little Dipteron fly, whose larval and 

 pupal stages I described in a paper published some years ago.^ At that 

 time I was unable to breed the imago and could only state that it was in all 

 probability one of the Phoridiie. During the late autumn of 1901 Mr. C. 

 T. Brues succeeded in rearing the adult insect from some larva? which I gave 

 him. He has since described it as Metopina pachycondyJoe ?■ Much of my 

 former account is here reproduced in a slightly altered form, together with 

 an enlarged photograph (PI. Y, Fig. 69) of the larvse and pupte of both host 

 and commensal. 



On October 27, 1900, 1 maile a short excursion to Mt. Barker, which 

 is hardly more than an hour's walk from the university at Austin, Texas. 

 The woods about the base and on the slopes of the elevation are favorite 

 nesting grounds for the large black Ponerine ant, Pachycondyla harpax 

 Fabr. In October this ant is rearing its second brood of larvae and pupae, 

 having completed the education of its first brood during June and July.^' 

 Wishing to continue some observations on the babits of Pachycondyla, I 

 dug u]D one of the largest colonies I could find and carried it home in a bag. 

 On transferring it to a Lubbock nest I took the census of the colony and 

 found it to comprise 25 worker ants, 13 cocoons, 8 mature larvae, 7 imma- 

 ture larvae, and a packet of eggs. While counting the larva^, which are 

 shaped like the well-known cucurbitaceous product known as the "crooked- 

 necked squash," and covered with hairy tubercles, I noticed that six of the 

 largest and one of the smallest presented an unusual appearance. Each of 

 these seemed to wear about its neck a huge collar — a kind of Elizabethan 

 ruff — consisting of a curled larva (PI. V, Fig. 69 .r). That this could not 

 be another ant-larva was apparent from a moment's examination. In all 

 cases it almost completely encircled the ant-larva in the region of the first 

 abdominal, or in some cases the metathoracic, segment. The posterior end 



> An Extraordinary Ant-guest. Am Naturalist, XXXV, 1901, pp. 1007-1016, 2 figs. 



2 A Monograph of tlie North American Phoridse. Trans. Am. Ent. Soc, XXIX, No. 4,. 

 1903, p. 384. 



3 For an account of the habits of this ant, see mv paper, A Study of Some Texan Ponerinse.. 

 Biol. Bull., Vol. II, No. 1 (Oct. 1900), pp. 1-31, figs. 1-10. 



