10 BULLETIN UNITED STATES GEOLOGICAL SURVEY. {T0I.Y. 



and 4 of an incli higii, compressed and its sides wrinkled perpendicu- 

 larly and its summit irregularly gaslied and toothed ; of a paler green 

 color than the leaf and more or less red on the side exposed to the sun 5 

 opening on the under side of the leaf by a long sUt-hke orifice ; inside 

 wrinkled perpendicularly into deep plates." The gall is always found 

 between two of the branching parallel veins, and those between which 

 it grows are generally drawn closer together than the rest. The corru- 

 gations and roughness, so characteristic of this gall, evidently result 

 from the lesser susceptibihty of the minute transverse veins to swell, 

 compared with the more succulent tissue of the leaf. There is always a 

 certain hoariness around the mouth of ihe, gall below, while the base of 

 the upper part is always contracted and compressed. 



BIOLOGICAL. 



The impregnated e^g of this species is also to be found during the 

 winter in exactly the same sheltered situations, in and under the bark 

 of the White Elm, as that of ScMzoneura mnericana. It is almost always 

 sheltered by the dry and somewhat wrinkled skin of the true female, 

 being seldom extruded, but occupj'ing the whole of the body (Fig. 2, &). 

 Occasionally the mother skin is more or less freed. The young stem- 

 mothers hatch from the winter ^gg about the same time, and are minute- 

 dark olive-brown specks, just visible to the unaided eye, and quite active 

 during pleasant weather, crawling nimbly about over the tree, till they 

 reach a tender leaf that is just unfolding, when they also settle upon the 

 under surface, and begin to feed on and fret the same. They doubtless 

 insert their beaks in various portions of the buds or expanding leaves 

 ere settling, since, before the gall begins to form, the little architect has 

 generally obtained twice the size it had when first hatched. By the 

 middle of AjDril, in the latitude of Saint Louis, the galls generally begin 

 to show, at first as slight elongate ridges on the upper surface, with 

 corresponding closed depressions on the lower surface. Upon drawing 

 apart the lips of the wrinkle beneath, at this stage of the growth of the 

 gall, the stem-mother, who still retains her glossy olive-brown appear- 

 ance, is seen constantly running back and forth in the cavity, and in- 

 flicting rapid punctures with her beak, the inner surface of her dwelling 

 being smooth and glossy, with a slightly blistered appearance, in con- 

 trast with the normal, more rough and pubescent texture of the under 

 surface of the leaf. The development of the gall is very rapid, and, 

 with favorable weather, the top part begins to bulge so as to give the 

 contracted appearance of the base, and the tooth-hke i)rominences be- 

 gin to appear by the third day. The inmate likewise grows apace. 

 After the first molt, she soon becomes more pyrifrom and paler, with 

 transverse rows of powdery secretion. She is less active, but still 

 marches about, incessantly fretting the surface with her short, stout 

 beak. A second molt takes place, and by the time the gall has fully de- 

 veloped, or about two weeks from the time it commenced forming, the 



