STUDIES ON APHIDID^. I * 



By John J. Davis, 



OFFICE OF THE STATE ENTOMOLOGIST, URBANA, ILL. 



Myzus elaeagni Del Guercio. 



I first found this aphid at Urbana, 111., November i6, 1907, 

 common on the ornamental Russian olive tree (Elasagnus angus- 

 tif olia) . At that time only the sexual forms (wingless oviparous 

 females and winged males) and the jet-black eggs were found, 

 the latter being common on the branches, along and in the axils 

 of the buds. A week later the same species was found on Shep- 

 herdia argentea. 



Early this year (January 18, 1908) a branch of Elaeagnus 

 bearing many eggs was placed in a warm insectary, the branch 

 being placed in water to keep it fresh. These eggs were first 

 noticed hatching February 2, fifteen days after being brought 

 into the warm room, and at about the same time at which the 

 leaf-buds began to expand. (The temperatures, taken with a 

 thermograph at midnight, 6 a. m., noon, and at 6 p. m., gave an 

 average of 59.2° F. for the period between the time the eggs 

 were brought into the insectary until they commenced hatching.) 

 In the warm insectary, the stem-mothers, or fundatrices, were 

 first observed producing young February 14, and on February 21 

 the first migrants of the second generation were found. These 

 migrants would usually fly from the original food plant imme- 

 diately upon becoming winged, and this, with the fact that I have 

 never found it on Elaeagnus during the summer, and that Pro- 

 fessor C. P. Gillette has collected it on thistle, indicates that this 

 aphid has a regular alternate food plant. 



Myzus elaeagni was first found in Europe and described by 

 Doctor Del Guercio in II Naturalista Siciliano, Vol. XIII, p. 

 197 (1894). I have not seen the original description, nor have I 

 examined European specimens, but specimens from Illinois were 

 sent to Doctor Del Guercio, who kindly determined them as his 

 M. elaeagni. In the Canadian Entomologist,Vol. XL., p. 17 (1908), 



* The object of these studies has been to learn the winter histories of httle- 

 known species of Aphididie, and to describe the various sexual forms here- 

 tofore unpublished; also to redescribe species which may have been only briefly 

 described. 



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