84 Zoologica: N. Y. Zoological Society [HI; 3 



thej' have also devoured all the beetle larvae since I found two 

 petioles each containing nothing but a pair of Scymnus pupse, a 

 few shrivelled remains of coccids and the kitchen-middens at the 

 ends of the cavity. The pupae were attached to the wall by 

 their caudal ends and with their longitudinal axis parallel with " 

 that of the petiole. They were of a waxy yellow color, with their 

 surface studded with short, blunt hairs. Several days later the 

 imaginal beetles emerged. They measured 1.7 mm. in length 

 and 1.2 mm. in width and were pale yellow, with the basal two- 

 thirds of the elytra, the meso- and metasternum and the median 

 third of the first and second abdominal segments fuscous. 



A much more abundant enemy of the the coccids is a peculiar 

 predacious Itonidid (Cecidomyid) fly, which Dr. Felt has de- 

 scribed as Diadiplosis pseudococci (Zoologica III, No. 8). The 

 larvae of this insect are orange red and are often found in clusters 

 of as many as eight to a dozen around groups of coccids. The 

 whole mass is covered by a tough, dense, white web, or tent, which 

 is spun by the larvae in such a way as to shut them and the coccids 

 ofl? from the cavity of the petiole and therefore from contact 

 with the beetles or their larvae. Thus secure from interference 

 the Diadiplosis larvae devour the coccids at their leisure, attack- 

 ing them from the ventral side where their integument is thin- 

 est and free from wax. The coccids are eventually reduced to 

 their dorsal integument. When mature the Diadiplosis larva 

 pupates where it has been feeding, often in the midst of a group 

 of young or full-grown larvae, and without orienting itself with 

 respect to the longitudinal axis of the petiole. Just before eclo- 

 sion the pupa forces its body, head foremost, through the silken 

 tent and projects into the cavity. The fly then emerges and prob- 

 ably either lays its eggs among any surviving coccids or emigrates 

 from the petiole and enters other beetle colonies. The adult fly 

 is a very delicate little midge measuring only 1.25 to 1.5 mm. 

 and of a reddish-brown color, with the abdomen red internally 

 and the sclerites somewhat infuscated. 



Considerable interest attaches to this insect, because, unlike 

 the great majority of Itonidids and the species noticed above (p.50) , 

 it does not make plant galls but is predaceous. The genus Diadi- 

 plosis was originally established by Felt ( 1911a) , for D. cocci Felt, 

 a species reared in the island of St. Vincent from larvae preying 



