THE CANADIAN ENTOMOLOGIST. 27 



cone was more regular on the latter. I have observed the same difference 

 between those found on willows and those found on silver-leaf poplars and 

 cottonwoods. I attribute it to the size and stiffness of the poplar leaves. 

 I have never met with the larva on the weeping willow. But to return to 

 its life history. 



On the morning of Saturday, July lo, I found on a leaf of Cottonwood 

 (Popuhis monilifera) a narrow white line about one-half inch long, which 

 was at once recognized as that of this species in a very early stage. On 

 holding the leaf up iil the sunlight the larva was visible in the mine ; it 

 was fiat, had membraneous, unarticulated and unarmed thoracic legs and 

 mouth parts of the " first form," with the head and thoracic segments a 

 little wider than the abdominal segments, and looked very much like a 

 Lithocolletis larva of the flat group in the same stage. (Nevertheless a 

 practiced eye will distinguish a Lithocolletis from a Gracilaria larva even 

 in this stage.) It was less than 8 m. m. long, and as I infer from many 

 observations on these small larvge and their mines, it was but a few hours, 

 probably about twelve hours from the egg. It extended the mine until it 

 was about 1.9 m. m. in length, and scarcely wider than the body of the 

 larva, and the mine looked like a portion of a Phyllocnistis mine ; then it 

 made a few digitate lateral branches, and the mine resembled a young 

 mine of Gracilaria robiniella in locust leaves ; then it connecte-d these 

 branches so that the mine became an irregular parallelogram about 1.9 

 m. m. long and 6 m. m wide ; and now, as stated by Mr. Stainton, the 

 mine was not unlike a young Lithocolletis mine, or a white blister on the 

 leaf. Like all larvae with trophi of the first form, it ate only a layer of 

 cells beneath the cuticle, not burrowing down into the pareuchyma. On 

 Tuesday evening, July 13th, about three to three and one-half days after 

 it left the egg, I found that it had very recently moulted whilst still in the 

 mine and that the body was now nearly cylindrical, that it had trophi of 

 the second form, and articulated thoracic legs each armed with a claw. 

 On Friday evening, July i6th (the larva now being about seven days, 

 within a very few hours, more or less, old) it was still in the mine, but not 

 feeding, and I think it had just moulted (2nd moult) ; but at an early 

 hour the next morning it had left the mine and was found on the leaf near 

 to the mine, and not feeding. I think it had very recently quitted the 

 mine. Three hours afterwards I found that it had gone to the tip of the 

 leaf which it had rolled up and was feeding in the roll ; and on opening 

 the mine two exuviae were found in it, one of which had the head and 



