4 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [ToJ.V. 



SOHIZONEURA AMERICANA, n. sp. 



[ Cuiiiuo- and o-uarling the leaves of the ^Vhite Elm ( Uhims americana), forming there- 

 by a sort of pseudo-gall. The curl made by a single stem-mother in the spring takes 

 the pretty constant form of a rather wrinkled roll of one side of the young leal; hut, 

 according as there is more than one stem-mother, or as several contiguous leaves are 

 affected, the deformation assumes various distorted shapes, sometimes mvolvmg quite 

 large masses of the leaves. ] 



BIOLOGICAL. 



There is a good deal of irregularity in tlie time of appearance of the 

 different generations, but the general history of this species, as I have 

 observed it for several years, is herewith given. There is much greater 

 difficulty in fully tracing the life-history of one of these small creatures 

 than might be supposed. They languish in confinement and ill bear 

 handling. To trace their growth and movements in a state of nature 

 requires vigilance and perseverance, and a great deal of time ; and I 

 have been fortunate, in my studies of this and the next species, in secur- 

 ing the patient aid of Miss M. E. Murtfeldt of Kirkwood, Mo., a lady 

 to whom I have akeady had repeated occasion to express my indebt- 

 edness. 



If, during the ^vinter, we carefuUy examine the cracks and cre\'ices 

 of an American or White Elm that was badly infested with this leaf- 

 curling species the previous summer, we shall be pretty sure to find its 

 impregnated egg— a minute, duU-yellowish, ovoid object, about 0.5"^" 

 long (Fig. 1, a), either free or still more or less effectually covered with 

 the parent's dry skin, which faintly shows the insections that char- 

 acterized the hving female. The same spring influences that cause the 

 ,leaf-buds to swell and open, likemse induce the hatching of this muter 

 iigg, and the little creature that issues from it instinctively crawls to the 

 more terminal twigs and branches, and settles upon the first tender leaf- 

 let it meets with. It constitutes the stem-mother, or first generation, and, 

 stationing itself on the under surface of the leaf, very soon causes the 

 same to swell and curl by the irritation and punctures of its beak. The 

 curl is usually from the lateral edge, and the more normal form it takes 

 is shown at Eig. 1, c. It is, however, very irregular, and takes on many 

 different forms, according as it is produced by one or several stem-moth- 

 ers settling on the same leaf, and as it affects a portion of one leaf only 

 or embraces several from the same bud. At first, pale yelloA^ish-red, 

 vxdth dark members, the stem-mother increases in size more or less rap- 

 idly, depending to some extent on the development of the leaf. Moving 

 about in her curled house, within which she is destined to live and 

 die, this stem-mother goes through her last moult, and attains maturity 

 about the twelfth day from the time of hatching. This period may be 

 lengthened by unfavorable weather, as an indefinite period of lethargy, 

 both of plant and insect, may ensue, after hatching, if the temperature 

 be too low. The number of molts I have not definitely ascertained, but 

 from analogy there will be three. Haviuii; attained matimty, she com- 



