APHID^E. 519 



APHID^E Latreille. The Plant-lice have antennae with from 

 five to seven joints, and generally longer than the body. The 

 ocelli are wanting, and the beak is three-jointed and developed 

 in both sexes. The legs are long and slender, with two-jointed 

 tarsi. The males and females are winged, and also the last 

 brood of asexual individuals, but the early summer broods 

 are wingless. Their bodies are flask-shaped, being cylind- 

 rical, the abdomen thick and rounded, and in Aphis and 

 Lachnus is provided with two tubes on the sixth segment for 

 the passage of a sweet fluid secreted from the stomach. The 

 wings are not net-veined, having few veins, which pass out- 

 wards from the costa. They are usually green in color, with 

 a soft powdery bloom which exudes from their bodies. 



Bonnet first discovered that the summer brood of wingless 

 individuals were born of virgin parents, hatched from eggs 

 laid in the autumn, and that the true winged sexes composed 

 the last generation, which united sexually, and that the female 

 laid eggs in the autumn which produced the spring brood of 

 asexual wingless individuals. 



Dr. W. I. Burnett gives the following brief summary of the 

 mode of development in this group. In the early autumn 

 the colonies of plant-lice are composed of both male and 

 female individuals ; these pair, the males then die, and the 

 females begin to deposit their eggs, after which they die also. 

 Early in the spring, as soon as the sap begins to flow, these 

 eggs are hatched, and the young lice immediately begin to 

 pump up sap from the tender leaves and shoots, increase rap- 

 idly in size, and in a short time come to maturity. In this 

 state it is found that the whole brood, without a single excep- 

 tion, consists solely of females, or rather, and more properly, 

 of individuals which are capable of reproducing their kind. 

 This reproduction takes place by a viviparous generation, there 

 being found in the individuals in question, young lice, which, 

 when capable of entering upon individual life, escape from 

 their progenitors, and form a new and greatly increased col- 

 ony. This second generation pursues the same course as the 

 first, the individuals of which it is composed being, like those 

 of the first, sexless, or at least without any trace of the male 

 sex throughout. These same conditions are then repeated, and 



