218 MONTANA EXPERIMENT STATION. 



Dr. Smith found that the second generation matures in nine or ten 

 days and that of chis series about three-fourths are winged ; that the 

 third series matures in about two weeks, less than one-half being 

 winged and that thereafter no more winged forms appear but that 

 seven series of parthenogenetic females in all appear before the end 

 of the season. The 8th and last series is made up of males and females. 

 Late in October, after the mating of the sexes, the females deposit 

 the eggs which remain on the trees during the winter. Figure 4, 

 right hand figure, shows an oviparous female. Figure 6, a male of 

 the oviparous generation. 



A part or all of the winged individuals of the early generations fly 

 to other trees. A winged partf^enogenetic female is shown at Fig. 5. 



The eggs are minute, glossy black objects, oval in shape. They 

 may be found on any part of the tree from the base of the trunk to the 

 tips of the twigs, and are usually more abundant in the crevices of 

 the bark and around the buds than on the exposed, smooth surfaces. 



A very large proportion of the eggs, probably upward of 90 per 

 cent, failed to hatch during the three years that we had the 

 species under special study. 



NATURAL ENEMIES. - - 



Of the various ratural enemies that feed upon the plant louse, 

 none is of greater value than the Fire-marked Lady-bug {Hyperas- 

 pis 5-signata) . Next in importance are certain species of syrphus 

 flies. Besides these we have observed a Braconid parasite, a small 

 fly that has not yet been named and the "Aphis Lion." 



After two years of close observation of the habits of this lady- 

 bug we are prepared to say that it is a very prominent factor in the 

 prevention of the aphis from becoming exceedingly abundant and 

 destructive. During the latter part of May and in June the beetles 

 were found in great numbers in the Experiment Station orchard, and 

 in various other orchards, running rapidly over the limbs and twigs 

 in search for the young aphids. The number they eat when in con- 

 finements is astonishing. 



In a previous paragraph we have called attention to the fact that 

 only a comparatively small number of stem mothers are to be found 



