26o MAINE AGRICULTURAL EXPERIMENT STATION. I913. 



the relative length of the joints, the wax glands of the apterous 

 generations other than the stem mother, and the antennal char- 

 acters of the winged females. The habitat and the species of 

 the elm concerned are also of much significance. 



The text figures of antennae in this bulletin are all drawn to 

 the same scale. 



Woolly Aphid oe Elm Bark. 



(Schizoneura rileyi. ) 



It is not uncommon to find the trunks and branches of young 

 elms with tender places in the bark closely packed with colonies 

 such as are shown in Figure 140. That Riley was correct in 

 describing this as a distinct species a further acquaintance with 

 the aphids leads me to believe. The stem mother has joint III 

 of antenna conspicuously shorter than those of the "leaf roll" 

 or "rosette." The wax glands of the second generation are of 

 a type similar to lanigera but with a tendency to a larger central 

 area. The antenna of the winged forms has joint III with the 

 aninulations less symmetrical than the other elm Schizoneurans, 

 and the grooves between the annulations are of more varying 

 depths. 



There are several matters of biological interest in connection 

 with this aphid which set it apart from any other species I know 

 at present. Winged forms are developed both in June and in 

 August, but both are developed on the elm. Whether they have 

 lost their function as migrants altogether, whether they simply 

 take wing to other elms, or whether there is a kink in the total 

 life cycle of this insect which we have not yet learned, I do not 

 know. 



On September 23, 1908, I made a collection of apterous vivi- 

 parous forms which gave birth to the true sexes. As in this 

 genus, so far as I know, the mothers of the sexual generation 

 are in other cases winged this seems peculiar. Individuals were 

 inclosed in vials with bits of cloth and the records carefully 

 taken so there could have been no mistake. 



The minute apterous oviparous females are born with a beak 

 w'hich is lost with the molt. They have a 5- jointed antenna. 

 Total length of body 0.8 mm. This form lays but a single egg. 



