459 



The eggs are deposited in the gall-hke cells of H. tritici external to 

 the host^ The average incubation period is about three days. Several 

 parasites may be found on one jointworm, but only one ever 

 completes its development. Larvae reared in glass cells become 

 fully grown in from 6 to 24 days, with an average of about 11 days. 

 The prepupal stage lasts from 1 to 6 days, with an average of 2 days, 

 and the pupal stage from 8 to 15 days, with an average of 10 days. 

 Normally, no males occur in the first generation, and the females 

 greatly outnumber them in the succeeding generations. The winter 

 is passed as a full-grown larva in the cells of Harmolita, the first 

 generation emerging about June and the second in July in Virginia. 

 The occurrence oi a partial third generation under field conditions 

 has still to be proved. Many larvae of the first generation do not 

 pupate the same season. Should the host of D. aureovindis be heavily 

 parasitised the latter may become a hyperparasite. 



Next to D. aureoviridis, the Pteromalid, Homoporus chalcidiphagus, 

 is the most important parasite of H. tritici in Michigan, Illinois, 

 Indiana, Ohio, Kentucky, Tennessee, and Missouri, although in the 

 Atlantic States Eurytonia sp. is probably of greater importance. 

 Although in certain districts as many as five generations occur annually, 

 their numbers are greatly reduced by hyperparasites, which include 

 Eupelmus allynii and D. aureoviridis. Homoporus chalcidiphagus 

 has been reared from field collections of Harmolita tritici, H. vaginicola, 

 H. secalis, H. hordei, Harris, H. elymicola, and H. atlantica. The eggs 

 are always found external to the host, as many as four or five being laid 

 in one cell ; but only one of these completes development. In glass 

 cells the incubation period varied from 1 to 4| days, with an average 

 of 2| days. The larvae become fully grown in from 5 to 25 days, the 

 average being about 11 days. Many larvae when fully grown become 

 quiescent for many months. The winter is passed as a fully grown 

 larva in the cells of the jointworm. The prepupal stage varies from 1 

 to 6 days, with an average of 2 days ; the pupal stage 5 to 23 days, 

 with an average of from 9 to 10 days. In Virginia the adults emerge 

 during the latter part of May and continue breeding until October. 

 Normally, the proportions of the sexes are about equal, but par- 

 thenogenetic breeding may occur, in which case the offspring are 

 males. 



Eupelmus alynii will probably breed on any species of Harmolita, 

 and as a hyperparasite was found breeding on Ditropinotus aureoviridis, 

 Homoporus chalcidiphagus, and Eurytoma sp. As with the other 

 parasites the egg is always deposited externally to the host. The 

 average incubation period is 2-4 days; the larval stage averages 

 16 days, the prepupal stage \1 days, and the pupal stage 21 days. 

 The winter is passed in the larval stage, and the adults emerge at the 

 end of April or beginning of May in Virginia. E. alynii is also a parasite 

 of the Hessian fly [Mayetiola destructor]. These parasites can only 

 be relied upon for partial control of Harmolita tritici owing to heavy 

 hyperparasitism. 



BvARS (L. p.). Notes on the Citrus-root Nematode, Tylenchulus 

 semipenetrans, Cobb. — Phytopathologv, Baltimore, Md., xi, no. 2, 

 February 1921, pp. 90-94"^, 1 fig. 



Tylenchulus semipenetrans, Cobb, is recorded as infesting nursery 

 stock of Citrus in Florida. There are apparently no symptoms by 

 which the presence of the parasite is indicated. Hot water treatment 



(4286) 2 H 2 



