FIRST SERIES: PEMPHIGUS ACERIFOLII RILEY. 11 



like their parents, they also deposit numbers of larva?, which in turn 

 reach maturity. 



Multiplication goes on in this way until a second series of migi-ants 

 is produced the following fall from the original settlers. However, 

 there remain again enough apterous females to produce a second 

 series of hibernating larva^, to produce an additional series of 

 migrants. A third series of migrants and hibernating larva? was 

 also traced. 



How long the vitality of the original stock will last it is impossible 

 at present to surmise, though it seems that multiplication may go 

 on indefinitely if the aphides are not exterminated by carnivorous 

 enemies or by parasites. 



The most active among the carnivorous enemies are the larva? of 

 the lyca^nid butterfly Feniseca tarquinius Fabricius; the larva? of the 

 lacewing fly Chrysopa sichell Fitch \^^G. quadrijni7ictata Burmeis- 

 ter] ; the larva? and imagos of two ladybirds, HippodaTnia convergeus 

 Guerin, and Adcdiu hipunctata Linnaeus; the larva and imagos of a 

 hemipteron, {Nobis) Pagasa fvsca Stein, besides the larvae of various 

 syrphid flies, which generally prove very destructive to these aphides 

 and frequently exterminate whole colonies. 



Internal parasites are thus far not known. 



Besides these enemies, there are various species of ants which are 

 mainly attracted to these aphides by the honey deAV ejected by them, 

 upon which they feed, while some of them even protect the aphides 

 against enemies by constructing tubes or tunnels of earth over and 

 around such colonies, leaving here and there a few exits open to 

 enable the ants to enter and leave. The ants which have been 

 observed to construct tunnels or covers over these aphides are Tapl- 

 noma sessile Say and Cremastog aster Uneolata Say; among those 

 which simply gather honeydew, Canhponotus pennsylv aniens De Geer, 

 Lasivs alienus Forster, and Monomorium minimum Buckley {minu- 

 tum Mayr) have been observed. 



EXTRACTS FROM NOTES MADE AT THE TIME. 



June 28, 1883. — Migrants from maple leaves, placed in a jar for 

 observation, deposited since yesterday a large number of larvae. KW 

 of them were provided with a long rostrum, which proved that they 

 were not the sexes of this species. 



Found to-day two colonies on leaves of maple near Rosslyn, Va., 

 and considered the migrants in these colonies at that time as being 

 identical with those of Pemphigus tessellata Fitch, though notwith- 

 standing that migrants were flying, I failed to observe any of them 

 or their larva* on any of the alders examined. However, after 

 placing infested leaves of maple with a branch of alder I found, 

 later on, that two of the migrants had settled on the alder leaves. 



