428 



Journal of Agricultural Research 



Vol. XV. No. 8 



narily pupate within 8 or 9 days after the host pupaiium is formed and 

 the adult parasites emerge in from 5 to 8 days later. A certain proportion 

 of the larvae reaching maturity each month of the year, however, pass into 

 a dormant state and may remain 'in this condition for from a few weeks 

 to several months, or occasionally a year. No doubt periods of long 

 drouth and scarcity of host material in Australia, in the localities 



Fig. ij. — Diachasma tryoni: Mature larva, lateral aspect. Length 3.1 mm. 



where this species is probably native, are frequent, and these conditions 

 may have necessitated such an adaptation. This parasite may thus 

 persist under very unfavorable conditions. With its introduction into 

 Hawaii this strong, inherent trait endures, even though climatic and 

 host conditions are ideal for continuous reproduction throughout the 

 year. The hibernating larvae look much the same as do other mature 

 larvae, although the body is somewhat contracted, shortened, and slightly 

 paler in color. During the entire period of dormancy the larva is capa- 

 ble of slow movement. 

 The dormant larvae are 

 not necessarily under- 

 nourished individuals. 

 In fact, hibernation has 

 been noted among in- 

 dividuals possessed of 

 large, fully nourished 

 bodies. No great va- 

 riation in the degree of hibernation has been noted to occur in fly larvae 

 from any special variety of fruit. The number of males produced from 

 hibernating material greatly exceeds the number of females. Between 

 August, 1916, and July, 1917, 663 males to 118 females emerged from 

 hibernating lots, ranging from i to 12 months old. 



Parasitized fruit-fly puparia placed in dry glass vials or jars yield a 

 much lower percentage in hibernation than do puparia left in the soil 



Fig. 13. — Diachasma tryoni: Greatly enlarged view of spines covering 

 surface of body of mature larva. Length, o.oi mm. 



