INSECTS AFFECTING PARK AND WOODLAND TREES 25 1 



elsewhere but for the sake of convenience may be summarized in this 

 connection. One species, H o r ma p h i s hamamelidis Fitch, produces 

 a pecular conical gall on witch hazel, which begins to develop at Washing- 

 ton D. C. about April 15. The winter eo^i:;; is deposited near th<^ 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 al):)ut April 15, become full grown by the middle of May and 

 produce young for three 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 l)irch, 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 sexual and wingless generation 

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

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

 third to fifth generation.s, the insect for some reason or other mimicking 

 Aleuroydes. 



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

 respects a more remarkable life history than the preceding. The earlic:r 

 generations subsist on witch hazel buds, wlilch gradually develop into 

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

 its life c}cle. The winter egg is deposited between the middle and the last 

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

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

 placed between or near the crotches formed by the twigs and |)etioles of 

 the flower buds or scars of fiower Inids or seed capsules. The stem motlu r 

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

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



