so AUSTRALIAN SUGAE-CANE BEETLES AXD THEIR ALLIES. 



Parasitic Insects. — Australia is also rich in these natural enemies of 

 the Scarabaeidffi. Those whose habits have already been studied some- 

 what belong to the IIymeno})terous families Seoliidie and Thynnidie, and 

 the Dipterous families Dexiidte and Taehinidie. The members of the 

 first three families are parasitic on the grubs; the Tachiuids here have 

 ■only been bred from the adult beetles. 



The Scoliid wasps are undoulitedly the most useful. Froggatt, in 

 "Australian Insects," states that about fifty species have been described 

 from Australia. Yet we have learned that their value is considerably 

 reduced by hyperparasites. Two of these were bred out on several 

 occasions by ]\Ir. Dodd — a Bombylid fly and a Rhipidophorid beetle. 



During our work in the Cairns district we have collected the follow- 

 ing species: — Campsonieris t-adula Fabr., C. tasmaxioisis Sauss., C. 

 ferruginea Fabr., C. carinifrons Turner, Scolia for)nosa Guer., Discolia 

 soror Sm., Liacos insulaiis Sm., Anthrobosca morosa Sm., and Tipliia 

 intrudens Sm. var. hrevior Turner. The first two and the sixth are very 

 common in our eanefields, the others being more rarely taken at flowers 

 in the uncultivated areas. 



During 1917 and 1918 we did considerable breeding work with the 

 first two Campsonieris species named above. This work has been fully 

 recorded in our Bulletin No. 13. During the day the males of these two 

 species of wasps frequently swarm in great numliers over the surface of 

 the soil in fields that are badly infested with grubs. Their mates, 

 normally working in the ground, are more seldom seen, though they are 

 probably equally numerous. On sunny mornings these female wasps 

 come out for a brief period, to feed upon the nectar of flowers or honey- 

 dew, where it is available. 



These wasps paralyse the grubs completely, in fact overdoing it at 

 times, so that the grubs frequently die too soon for the larvae of the 

 wasp to develop. And, again, it was interesting to observe that these 

 parasites appeared to have a natural love for killing ; when put in soil 

 with several grubs they were usually not satisfied until they had stung 

 the lot, though in no case was more than one laid upon. 



Since the climate in the Cairns district is so tropical — the tempera- 

 ture even on the coldest winter nights seldom dropping to 40 deg. Fahr. 

 — these wasps are active the year round. The complete life-cycle for the 

 wasps studied during spring, summer, and autumn ranged from forty to 

 sixty days, and though the development would naturally be somewhat 

 retarded in winter, there is no question that they continue to breed at 

 that season. Hence there are probably four complete ])roods annually, 

 corresponding somewhat to the four seasons. 



Fortunately these parasites are able to adapt themselves to several 

 hosts, so that they are able to find some species of grub available at 

 almost every season. We discovered by breeding work, however, that 

 the grubs must be closely related, for the wasps took no notice of those 

 belonging to a different sul)family. 



The importance of nectar for these wasps cannot be over-estimated. 

 They will not stay and work where they cannot find a supply of this 

 sweet food, and they would not lay in cages without it. Hence, in order 

 to attract and maintain a good supply of these friends in the vicinity of 

 igrubby fields, attention must be given to this problem. Corn grown in 



