ADJUSTMENT TO NEW HOSTS. 



67 



striking about the nature of the record that ^Mr. Cushman was sent 

 ininiediutcly to Victoria to study tlio surroundings of this field and 

 report upon tlic possible reasons for the higli percentage of parasitism. 

 >lr. Cushman reported after considerable study that there were 

 only two factors which, it seemed to liim, might have an influence 

 upon the parasites of the boll weevil. The first factor was tlio com- 

 plete lack of fruit upon the huisache trees (Vachellia famesiana) 

 which is the normal food of Laria sallxi. The second factor noticed 

 was the absence of flowers on the Callirrlioe involucrata, the liost of 

 Anthonomus fulvus. Mr. Cushman reasoned that the point would be 

 proven if we should rear from the boll weevil some of the cliaracter- 

 istic parasites of cither this or the other species. As a result of 

 rearings from the material collected in this field, the principal par- 

 asite was Microhracon mellitor, the typical boll weevil parasite, but a 



Seasonal /wtavoa/ OF HOSTS By Cajvlaccus hunteri Craw/idrd. 



So^SOM^t ROTAT/OTJ OF HOSTS BY CFRAM8yCOB/US CyAMCFPS ASHMFAD. 



Tacm 



'ICWBUS S, IK 



AmTHONO. ^aS CRAlJoiS BOHEM. w 



Trichoba'^is texawa i.sCo^T£ 



l/XUS SC^OBICOLI./^ B omemM/ 



'^lERCE 



S/WCRACAAX rUBE-^UIATUS 



yPTERELUIS 



TrcH 'US 



QUAORi 

 SORDIpUS 



Trichcbaris CO 



VIPACTA CASEy 



AllTHONOMLS GRAA/C'S BOHEI^AN 



Aun lONOMUS 



^LBOPIlOS7S DiETZ 



TRICH06ARIS TEXA/VA lEGO/VTe 



LiXUS Sc ■RCBICOL L 



t 



SmICI 'AUiAX 7t eERCOlATtIS Pepct 



Fig. 15.— Diagram illustrating the seasonal rotation of hosts of Calolaccui hunteri and Ceramhycobius 



cyaniceps. (Original.) 



species which is also a typical parasite of Anthonomus fulvus. It 

 is probable that the latter species furnished some of the Micro- 

 bracons for this infestation. The next most important species was 

 Ceramhijcohius cusJimani, a typical parasite of Laria sallxi and of 

 Arxcerus fasciculatus which breeds in the fruit of the chinaberry tree 

 ( Melia azederach) . In addition to this species, this same field yielded 

 3 other new parasites of the boll weevil, 2 of which are known to 

 be parasites of the Laria. These were Eurytoma sp., Spilochalcis sp., 

 and Larioplmgus texanus. 



To illustrate tlie divergence of habits among parasites the host 

 relations of Catolaccus incertus may be cited. This parasite attacks 

 several species of Laria (Bruchus) which are internal seed eaters and 

 pupate in their feeding cells; such weevils as Zygoharis xantlioxyli and 

 Auleutes tenuiyes, which are seed or bud feeders and pupate in the 



