302 EXPERIMENT STATION— BULLETINS. 



examining the lice, or by studying the figure, these lice have long, seven- 

 jointed antennae — the horn-like organs appended to the head, and the winged 

 lice have simple veined wings. The main vein of each wing is branched. 

 There are four branches in the front or primary wings. The outer one is 

 strongly curved and the next one branches twice. There are two simple 

 branches on the posterior wing. This style of venation is characteristic of 

 the genus aphis. We also note (see Fig.) that there are two short spine-like 

 projections, black in the grain aphis, on the third part of the abdomen. 

 These are the nectaries or honey tubes, so called because there frequently 

 exudes from them a nectar which attracts ants and bees to these lice. Just 

 now (June 26, 1889) a species of plant louse on our Norway spruces are 

 secreting nectar so profusely that in the early morning it stands on the 

 leaves in drops, so that it can be tasted. It seems very pleasant to the taste, 

 and is giving the bees a fine harvest. This peculiar physiological character- 

 istic serves the louse in this way : by attracting ants, wasps and bees, the 

 birds and insect enemies of the lice are frightened away. I find that the 

 oats and wheat are visited by ants that the nectar secreted by this grain 

 aphis may be secured. The beak of this grain aphis is strong, dark in color, 

 and about one-third the length of the body. With this the louse sucks the 

 sap and devitalizes the plants. The feet and joints of the legs and also the 

 antennas are dark or dusky in color. 



The color in these lice varies greatly. Early in the season while they are 

 on the leaves or stalks they are green. This is the color now of all healthy 

 lice on the oats. After they migrate to the heads they often turn yellowish 

 green and even rust red, though I find that now the green color prevails even 

 with the lice which are gathered thickly about the kernels. Some of the 

 winged lice are very dark, almost black. In these the legs are nearly all 

 black. It is probable that the nature of the food affects the color. As the 

 berries mature I think the yellow and red colors will prevail to a larger de- 

 gree. 



REPRODUCTION" OF THE LICE. 



The reproduction of plant lice is very curious. Late in the season we find 

 both sexes. This is the only time that we find males. The sexes now pair, 

 and eggs are laid about buds, in crevices, or where they will best survive the 

 winter. In the spring only females hatch from these eggs. These do not 

 lay eggs, but each gives birth to from three to five lice each day. In about 

 four or five days these young lice begin to produce living lice, each contrib- 

 uting daily its four or five new lice to help on the general devastation. Such 

 early and rapid breeding implies great nutrition, and we easily understand 

 why the plants wither and dry up. We also see how the lice become so quickly 

 numerous and widespread. Calculation shows that in less than a month, if 

 no lice died or were killed, a single louse might be the progenitor of more 

 than several million lice. To follow the number further defies comprehension. 

 Many have written me : "We can not imagine where the lice could come from 

 so quickly and rapidly." The above fact explains this physiological riddle. 



WHY SO NUMEROUS THIS YEAR. 



This is not the first season that this Aphis avenge has come like a destroy- 

 ing flood upon the grain fields. In 1861 the lice swarmed upon the cereal 



