BIOTIC ASSOCIATIONS OF COCKROACHES — ROTH & WILLIS 35I 



Saudi Arabia; some 15 percent of the oothecae of P. americana and 

 P. australasiae collected in October in Trinidad were parasitized; a 

 later collection (March) was 34 percent parasitized; a small sample 

 of P. americana oothecae was 65 percent parasitized. The oothecae 

 collected in Saudi Arabia in March were 20 percent parasitized. 

 Plank (1947) found that the eggs of the American cockroach in 

 Puerto Rico (probably in laboratory cultures) were so heavily para- 

 sitized by T. hagenowii that he had to use P. australasiae for experi- 

 mental purposes; in 1950 Plank stated that more than 50 percent of 

 American cockroach oothecae were parasitized. 



Fahringer (1922) stated that Prosevania punctata could be used to 

 eradicate cockroaches, but he did not test his hypothesis. Marlatt 

 (1902) felt that the usefulness of Evania appendigaster in biological 

 control was impaired by Tetrastichus acting as a hyperparasite (see 

 footnote 6, p. 236). However, Wolcott (1951) stated that in Puerto 

 Rico E. appendigaster is quite abundant and is a factor of considerable 

 importance in controlling cockroaches. Kadocsa (1921) stated that 

 Brachygaster minutus and Evania appendigaster were not important 

 in the biological control of cockroaches. These general statements 

 are not supported by experimental evidence. 



It is likely that the smaller wasp egg parasites are more effective 

 than the evaniids in controlling cockroaches. Only one evaniid de- 

 velops in a parasitized ootheca, but many individuals of the other 

 wasps develop in one ootheca and the number of females that emerge 

 is usually large. However, Cameron (1957) concluded that, with a 

 parasitism rate of 25 to 29 percent and three to four generations a 

 year, against one or less for the host, Evania appendigaster in the 

 areas where it is established is a valuable control agent. 



The use of specific egg parasites to control cockroaches has not been 

 attempted extensively. Cros (1942) liberated a species of Tetrastichus 

 {=Eulophus sp. ; see p. 254) in his home in Algeria to control the 

 oriental cockroach ; as far as we know, he did not report the parasite's 

 effectiveness in reducing the cockroach population. According to 

 Zimmerman (1948) Coniperia merceti, when accidentally imported, 

 practically wiped out Siipella supellectilium in parts of Hawaii ; he 

 claimed to have controlled the brown-banded cockroach in a store 

 building with this parasite. In some parts of Honolulu, almost 100 

 percent of the oothecae of this cockroach were parasitized (Zimmer- 

 man, 1944). We (1954b) ran some simulated field tests in which we 

 liberated Tetrastichus hagenowii in rooms artificially seeded with 

 oothecae ; from 28 to 83 percent of American cockroach oothecae and 



