195 



in newly hatched larvae of their hosts, and Blepynis indeed 

 apparently never attacks the later stages although issuing from 

 nearly full-grown hosts. It is at once obvious that Coccids in 

 their earlier stages might more easily escape the attention of 

 the careful plant-grower or importer and thus be allowed to 

 become established in a new locality. If some are parasitized 

 the establishment of both host and parsite is thus accomplished 

 at the same 'time. 



T'arthenogenesis has also played a large part without much 

 doubt in helping the establishment of certain of our immigrant 

 species. As a general rule it may be stated quite confidently 

 that all Encyrtidae, and for that matter most if not all Chalci- 

 doidca, in so far as their habits have been investigated, are able 

 to reproduce parthenogenetically under stress of necessity. 

 Probably most species of Encyrtidae produce only males when 

 the reproduction is parthenogenetic, and in ease of the usual 

 method of reproduction they produce in different species a 

 \ariable proportion of both males and females. Before study- 

 ing the habits of our local species I had never verified the 

 existence of any other method of reproduction among the 

 Encyrtidae, and was surprised to find that certain of our spe- 

 cies are .regularly thelyotokous in reproduction. In Adelencyr- 

 tns odonaspldis, Blepyrus mexicanus, PJncyrtiis infelix, Pau- 

 r'ldla pevecnna and Sarunoluiii ainericaiiiini thelvotoky is the 

 regular means of reproduction and males ar(- rarely ])r(>(luced. 

 being in fact entirely unknown in case of Adelcnci/rlKs and 

 Saronotum. I have reared the Paiiridid through many genera- 

 tions without finding any makvs, and have in fact seen but a 

 single male reared l)y Mr. Ehrhorn several years ago. I have 

 likewise reared Blepyrus througli several generations and was 

 able to find males of this species only by examining some bean 

 vines at the Sugar Planters' Experiment Station at a time 

 when both host and ])arasite were unusually abundant. Of 

 Encyrius infelix I was fortunate enough to rear a single male 

 in a small series obtained in 1916, and this is the only male 

 specimen that I have seen out of numeroiis specimens examined 

 from various parts of the woild. Miss Embleton in her work 



