286 



so far as possible, illustrations of at least five stages of each species, viz : 

 (1) The egg; (2) the apterous viviparous female ; (3) the winged vivip- 

 arous female; (4) the male; and (5) the oviparous female. Of course, 

 an acquaintance with these forms does not necessarily involve a knowl- 

 edge of the complete life-history of a given species, especially in those 

 cases where seasonal migrations from one host plant to another occur, 

 but such information will at least furnish a basis for systematic mono- 

 graphic work, and will also prove helpful in tracing the life-cycles. 



The studies upon which this series of contributions is based were 

 undertaken especially to learn the autumn and winter history of Ameri- 

 can Aphididse. Previous writers have as a rule been content to de- 

 scribe the viviparous forms, and until recently our knowledge of the 

 sexed forms and hibernating stages of nearly all our species was very 

 limited. 



The observations upon which the present paper is based were made as 

 a part of the work of the Ohio Agricultural Experiment Station, mostly 

 upon the station farm during the autumn of 1890. The drawings for 

 the illustrations accompanying it were prepared by my assistant. Miss 

 Freda Detmers, from freshly killed specimens, while the descriptions 

 are all drawn up from the living insects. 



The Sycamore Itachnns {Lachnu8 plat anicola 'Riley). 



This species was described in 1883 by Dr. C. V. Eiley in a short note 

 in the American Naturalist (vol. 17, pp. 197-198). It is said to have 

 been excessively abundant in 1882 on Sycamore trees over a large part 

 of the United States. The male, oviparous female, and egg are very 

 briefly characterized. 



During the present season this insect has been extraordinarily abun- 

 dant in central Ohio. During the summer and early autumn months 

 nearly every Sycamore tree was thickly infested, and the eggs were 

 deposited on the bark of the twigs and branches in enormous numbers. 

 The sexed forms appeared late in September and throughout October. 

 The deposition of eggs began early in October, continuing for more than 

 a month. 



The different stages of the Sycamore Lachnus are shown much mag- 

 nified at Plate 1. Fig. 1 represents the winged male. Fig. 2, the apter- 

 ous viviparous female, Fig. 3 the winged viviparous female, and Fig. 

 4, the eggs. All except the eggs are shown much magnified, the 

 straight line at the right indicating the natural size of each. 



Like the other species of the genus these insects have the habit of 

 waving their long hind legs in the air when alarmed. 



DESCRIPTION. 



Apterous viviparous female (Plate 1, Fig. 2, 2a). — Body 6 millimeters long by 

 3.5 millimeters wide across middle of abdomen ; autennte, 3 millimeters long; pos- 

 terior legs, 9 millimeters long. 



General color light brown, with a glaucous bloom. Antennae, eyes, most of head, two 



