Sept , 1909.] Hayhurst : Two Species of Hyalopterus. Ill 



that aphids can stand considerable freezing in the fall, if their host is 

 hardy, while other individuals of the same species on tender plants 

 perish with the death of the host. 



Since Dacfylis glomerata is an introduced grass from Europe, the 

 aphids must infest other grasses in this country from which they have 

 gone over to orchard grass unless they were introduced with this 

 plant ; but the species has apparently not been noticed by European 

 writers. 



I have never seen this aphid attended by ants. Two species of 

 hymenopterous parasites were reared from the wingless vivipara;. 

 Lysiphlebus cerasaphis Fitch turns the host brown as in most parasit- 

 ized aphids, while the other, Ephedrus sp., probably plagiator 

 ( =^ parctconiis) Nees causes the aphid to become coal black. They 

 were collected at Forest Hills, Mass., May 22-23, 1909. I am in- 

 debted to Mr. C. T. Brues who kindly determined these parasites 

 for me. 



The wingless viviparje of Hyalopterus dactylidis are remarkable in 

 possessing a pronounced outpushing of the posterior lateral angle of 

 the prothorax (Fig. 9). I have examined many specimens both liv- 

 ing and in formalin and find this character normal and not especi- 

 ally variable. It is present, but less conspicuous, in the wingless 

 viviparai, fall forms, of H. aquilegice-flaviis on columbine. It is not 

 discernible in the youngest larvae with 4-jointed antennae, but is very 

 evident in half grown larvae (i mm. long) with 5 -jointed antenna. 

 Judging from the few specimens of the winged vivipars which I have 

 seen the third discoidal is apt to be very variable. I have at hand 

 only nine specimens, three of which have the usual type of venation 

 in the Aplndlnce on both wings (Fig. 10). The other six are as 

 follows : 



(a) One wing with unbranched third discoidal as in PempJiigus, 

 the other wing with irregular atrophied branches (Fig. 10, c-d). 



{/>) Third discoidal 2 -forked in one wing, but i -forked in the 

 other as in Toxoptera (Fig. 10, a'). 



(<:) Two specimens with all the third discoidals 2 -forked, the 

 second fork close to the margin as in Aphis {Siphocoryne) avence Fabr. 

 (Fig. 10, l>). The vein figured also shows a supernumerary branch 

 near the second fork. 



{d) One vein single, the other i-forked. 



{e) Both third discoidals i -forked, but in one wing the first branch 



