INSECTS AFFECTING PARK AND WOODLAND TREES 25 1 



elsewhere but for the sake of con\'enience ina)' he summarized in lliis 

 connection. One species, Horinaphis li a m a ni c 1 i tl i s I'itcli, jiroduces 

 a pecuhir conical gall on witch hazel, which begins to develop at \\'ashin(r- 

 ton D. C. about April 15. The winter egg is deposited near the' base of 

 the buds or leaf scars and resembles those of the ordinary apple aphis. 

 The stem mothers are black, fringed and adorned with waxy rods and 

 appear about April 15, become full grown by the middle of May and 

 produce young for thn>e or four weeks. The second or migratory genera- 

 tion completes its development in 6 to 20 days, is winged and flies from 

 the last of May to the last of June and later to the birch, where a third 

 generation is developed on the underside of the foliage, which in the fourth 

 and last stage resembles an Aleuroydes, being oval, flattened and fringed 

 or adorned with waxy rods. The fourth and fifth generations are like the 

 third and also occur on the birch. The sixth, however, is more like the 

 normal plant louse. It is clothed in its second to fourth stages with a 

 dense, evenly shorn waxy secretion and matures into normal appearing 

 aphids, which migrate back to the witch hazel from the last of August 

 to early October, where the seventh or se.xual and wingless generation 

 develops on witch hazel, each female producing from five to 10 eggs. It 

 will be notetl in this species that there is a marked difference in form in the 

 third to fifth generations, the insect for some reason or other mimicking 

 Aleuroydes. 



The other form, H a m a m c 1 i s t e s s p i n o s u s Shinier, has in some 

 respects a more remarkable life history than the preceding. The earlier 

 generations sul)sist on witch hazel buds, which gradually develop into 

 conspicuous spiny galls, and two years are required for the completion of 

 its life cycle. The winter egg is deposited between the middle and the last 

 of June and hatches about the last of May or early the following June, 

 nearly 1 1 months being spent in this form. These eggs are commonly 

 placed between or near the crotches formed by the twigs and petioles of 

 the flower buds or scars of flower buds or seed capsules. The stem mother 

 settles on the side of the young bud against the twig, the opposite side 

 grows rapidlv and soon arches over and finally incloses the plant louse, 



