96 ILLINOIS BIOLOGICAL MONOGRAPHS [414 



Several species have been examined. None of the material has been 

 identified altho the following larva may belong to /. suhgregarium. 



Isodyctium sp. 1. — Length, 15.5 mm.; head, 1.5 mm. wide; head marked 

 on vertex and front with large confluent brownish spots, those on front 

 sometimes separate; body uniformly greenish; legs concolorous with 

 body, femur subequal in length to tibia; spines blackish, very long and 

 furcate, with large proximal end, those ventrad of spiracular lines whitish; 

 those one-half as long as head are wide as seen in profile; prothorax with 

 spines, 2-2-2-1:2-2:1:2; third abdominal segment, 2-2-2:1:2-2-2:2-1:1-1; 

 tenth abdominal tergum, 2-1:2:2, the mesal pair sometimes with confluent 

 bases; maxillary palpi, (4, 2), 3, 1 ; labial palpi, 1,2; ultimate stage: entirely 

 whitish, vertex pale brown, third abdominal segment with five distinct 

 annulets, setiferous but not spinose; on oak; M-6. 



Subfamily Fenusinae 



Larvae (Fig. 21) very small; body semicylindrical, venter flattened, 

 depressed, tapering caudad, glabrous; segmentation distinct; annulation 

 indistinct; third abdominal segment with either one or apparently 2-4 

 annulets; thorax slightly swollen, prothorax sometimes with dorsal and 

 ventral shields; legs small, short, apparently with four segments, spreading 

 cephalo-laterad; larvapods on abdominal segments 2-8, vestigial, merely 

 mound-like; anal larvapods obsolete; tenth abdominal tergum glabrous 

 without suranal processes or caudal protuberances, sometimes with small 

 mesal projections; suranal and subanal lobes glabrous; liead sparsely 

 setiferous, depressed, subtriangular in outline, wedge-shaped in profile 

 narrower than thorax and overlapped on caudal third by prothorax; ver- 

 tical furrows wanting; antennae apparently with single segment; antacoria 

 large; ocellarae minute, located dorso-caudad of antennariae; ventral 

 glands wanting; glandubae wanting; spiracles indistinctly winged; cuticle 

 sometimes with microscopic but distinct chitinized dentiform spines; 

 larvae, leaf-miners. 



The Fenusinae is a small subfamily represented by four genera in the 

 Nearctic region. Systematists have always considered this group as 

 closely related to the Scolioneurinae and Blennocampinae. MacGillivray 

 is the only one who would assign them subfamily rank. Konow listed three 

 European species, dohrni, ulmi, and pumila, under the old generic name 

 Kaliosysphinga. The first two are now considered as types of distinct 

 genera. They have been introduced into this country and are liable to do 

 considerable damage at times. The genera studied are separable as follows: 



GENERA OF FENUSINAE 



Caudal end of body rounded, without a mesal suranal protuberance; sternum of ninth abdom- 

 inal segment with a pair of swellings covered with distinct microscopic dentiform spines: 



