74 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 57. 



THEISOA CONSTRICTELLA Zeller. 



Plate 7, fig. 37; plate 9, figs. 54, 55, 56. 

 Theisoa constrictella Zeller, Dyar, List N. Amer. Lep., No. 6130. 



On a few elms along the river bank at Great Falls, Virginia, Fr. 

 DeGryse and the writer found most of the foliage attacked by a small 

 caterpillar which makes a web on the underside of the leaf between 

 two of the branching ribs, drawing the leaf together slightly and feed- 

 ing on that part of the epidermis covered by the web. It also con- 

 structs a small tube of frass within the web into which it retires when 

 not feeding. The work is locally common at Great Falls, but I have 

 not seen it on the elms elsewhere in the vicinity of Washington. A 

 quantity of infested leaves were collected during September, 1915, 

 and placed to rearing (under Hopk. U. S. No. 13937). The insects 

 pupated during October in small, smooth cocoons attached to the 

 fallen leaves and overwintered in that stage. During the following 

 July (1916) several moths issued. These proved to be Zeller's species. 

 The general structural characters of the larvae show very close rela- 

 tionship to Clirysoyeleia. In larval habits the two genera are also 

 very similar except that Theisoa does not mine the leaf. This, as 

 well as its more specialized head structures, would point to Cliryso- 

 peleia as a later development. As nothing has been previously pub- 

 lished on the earlier stages of the genus, a fuU larval description is 

 given. Unfortunately no pupae were saved, so I can not describe 

 that stage. 



General characters. — As in Chrysoyeleia except as foUows: Cro- 

 chets biordinal; pro thorax with Ila on the level of la, anterodorsad 

 of Ilh, closer to Ilh than to la, pmicture y directly caudad of la, lie 

 equidistant from Ih and Ic, lie, Ic and Ih forming an isosceles tri- 

 angle; meso and meta thorax with setae groups / and 7/ not closely 

 approximate, ///, IV, and V not in a longitudmal or transverse line 

 on segment, rather forming an obtuse angle ; proleg bearing segments 

 of abdomen with II remote from and slightly lower than I; abdominal 

 9 with II, I, and /// not in a vertical line, triangularly grouped, 

 / cephalad to and nearly equidistant from II and ///, VI present. 



Head ovoid; oval in outline viewed from above; as long or slightly 

 longer than wide ; incision of dorsal hind margin less than one-fourth 

 the width of the head; distance between extremities of dorsal hind 

 margin a trifle less than one-half the width of the head. Frons 

 reaching only to just beyond middle of head; adfrontal ridges sinuate, 

 nowhere straight; longitudinal ridge nearly as long as frons. Pro- 

 jection of dorsal margin over ventral about half the diameter of the 

 head. Frontal punctures and frontal setae on nearly the same level; 

 puncture Adfa not distinguishable. Anter or setae of epicranium 

 forming a slightly obtuse angle; Al and A2 fairly well separated 



