October, '14] ILLINGWORTH: TACHINID PARASITES 391 



they were all collected in fields where the flies were abundant. I 

 estimated that if I could get these 1,000 grubs safely to Fiji, enough 

 flies would emerge to fully stock several cages, and have a fair colony 

 to liberate in the field at once. 



During the voyage about 100 of the flies emerged from the puparia 

 which had been found in the borer cocoons. It is rather interesting to 

 note that the emergence of the flies invariably took place in the morn- 

 ing. If the weather was warm, the first flies appeared about daylight, 

 and they continued to emerge for about three hours; on cool mornings, 

 the emergence sometimes did not begin before 10 o'clock. 



All of the flies that emerged during the trip to Suva were put into 

 inverted glasses, on sheets of clean white paper. They were daily sup- 

 plied with fresh slices of cane and bits of cotton batting saturated in 

 water. By giving them moisture in this manner I avoided the difficulty 

 of having them injure themselves by getting wet, as they invariably do 

 when in close confinement. Even a drop of water on the paper soon 

 resulted in several being upset and stuck in it. 



By using greater care than one would need to give to a lot of babies, 

 I was able to save practically all the flies that emerged en route. 



On reaching Suva, the flies that were already emerged were quickly 

 taken to the nearest of the plantations — twelve miles away, at Nausori, 

 on the Rewa River — where cages were already prepared. Half of the 

 flies were placed in one of the cages, which had been stocked with canes 

 containing borer grubs; the other half were placed directly in one of 

 the badly infested fields. This part of the island has a heav}" annual 

 rainfall and the cane is ripened with some difficulty. Since the failure 

 of three previous attempts to introduce these Tachinid parasites at 

 Nausori was attributed to the excessive hum.idity, we decided to take 

 the greater part of our parasites to a drier section. We found Nadi 

 district, which is situated about 100 miles from Suva, at the far end 

 of the island, most perfectly suited to our needs. Two cages (Plate 10, 

 Fig. 1.) were at once completed and stocked with grub-infested cane, 

 about 50 flies were placed in each cage. 



The remainder of the parasites which were, by this time, in the 

 form of puparia, we decided to at once place in the field to emerge. 

 The jars containing the puparia and damp frass were placed in a 

 shelter and protected from ants, in a way similar to that used in Hawaii. 

 We were unprepared, however, for the disaster that awaited us when 

 we visited the field on the following morning^the rats (or mice) had 

 gotten into the box and clawed out all the frass and puparia from the 

 jars, destroying most of the flies. This left us with only our cages to 

 fall back upon, but we had had the experience,^the liberating boxes 

 must have mouse-proof screens. 



