71 



Syrphus Hies were not abundant until Ma}^ HO, wtien they were very 

 common and ovipositino-. Nine-tenths of them were Syrphus ameri- 

 cana Wied,, and the remainder SplKEVophoria cylindrica Say. and 

 Allograpta oUiqua. Bassus Imtotorius Fab. was also quite common, 

 and later almost all of the puparia of A. olllqua were found parasitized 

 and the parasites bred from them. On June 11 no syrphus flies were 

 seen, but on the 18th a third brood had appeared and were swarming 

 over the field, a half dozen being seen often on a couple of feet of vines, 

 and making- a very audible buzz over the whole field. 



Ladybird beetles and larvoe were common throughout May, but not 

 until the second week of June did the}^ become abundant. I could 

 not determine any regularity of the broods of these insects. Coecl- 

 nella 9-notata, Rippodamia convergens, H. glacialis, Megilla waoidata, 

 O. sanguinea, and Adalia hipunctata were all common, the first 

 named being the most common. Though the larvas of these ate large 

 numbers of pea lice between June 1 and 18, they were too late to 

 prevent the worst injury. Chrysopa oculata was common, but was not 

 nearly as valuable as the other predaceous insects. Altogether, the 

 enemies of the lice appear too late to prevent the bulk of the injur}^, 

 and as the same was true last year, it seems impossible to place any 

 dependence upon them. It seems evident, however, that the lice are 

 attacked by a parasite while still in crimson clover (parasitized lice 

 were also common on red clover), but are not parasitized until they 

 have been on peas for some time. Is it not possible the sudden 

 appearance of the lice last year may have been due to the severe win- 

 ter, which killed off the parasites and other enemies which usually hold 

 the lice in check on the clover and so reduce their numbers that but 

 few of them spread to peas ? 



The very sudden appearance of this new species last year was a 

 unique entomological surprise. Where it came from was a question. 

 It would seem to me that the original food plant of the pest was clover 

 and probably crimson clover. It is true that crimson clover is not 

 grown in the North where the louse was found destructive last year, 

 but it is entirely possible that it may have spread from sections in 

 which crimson clover is grown to red clover in these localities, but have 

 been held in check by its parasites, and remained unnoticed. Further- 

 more, the insect enemies of red clover have at various times received 

 study without this species having been previously noted. On the other 

 hand, there seems to be good evidence that the louse has been on crimson 

 clover for several years. One of our best farmers, Mr. Frank Bancroft, 

 of Camden, Del., tells me that he has seen what he judges to be the 

 same louse on crimson clover for at least six or seven j^ears. In 1890 

 crimson clover grown upon an experimental plot at the Delaware Sta- 

 tion became so badly infested with a plant louse that it was feared it 



