106 ILLINOIS BIOLOGICAL MONOGRAPHS [106 



Family Thyatiridae 



Head vertical, wider than high; front small; adf rentals distinct; 

 no secondary setae; labrum usually notched to about two-thirds its 

 depth, sides of notch parallel. Body cylindrical, not bearing secondary 

 setae; primary and subprimary setae arranged as described for Epi- 

 plemidae except that the Pi group on the prolegs consists of three setae 

 only and of at least two setae on segments 1, 2, 7, and 8. Ventral pro- 

 legs bearing biordinal crochets in a curved mesoseries; anal prolegs 

 reduced to one-half or two-thirds size of ventral. 



Hdbrosyne rectangulata has the head shining and the Pi group 

 on the mesothorax and metathorax bisetose. In H. scripta the head is 

 more or less dull and minutely rugose, the dorsal half of the abdomen 

 bears diagonal stripes, and the Pi group on the last two thoracic seg- 

 ments is unisetose. 



Pseudothyatira expultrix and P. cymatophoroides each show a dull- 

 and rugose head and unmarked body. The Pi group is bisetose on each 

 thoracic segment. 



Family Notodontidae 



Larvae of this family are usually identified at a glance by their 

 peculiar decoration and shapes. A student of the larval stage can not 

 accede to Hampson's view that the arctians, noctuids, and syntomids 

 are specialized modifications of the notodontian type, or that Notodon- 

 tidae are a generalized family. All the species have secondary setae 

 on the sides of the prolegs and specialized anal prolegs, thus departing 

 widely from the generalized condition retained by Noctuidae. 



Many species of the subfamily Notodontinae will trace to Noctuidae 

 in any tables hitherto published. The setiferous prolegs will serve to 

 distinguish in most of these cases. Other characters are given in the 

 table for the separation of the families. The subfamilies may be recog- 

 nized by the following key : 



a. Body bearing numerous secondary setae, obscuring primary ones; 

 anal prolegs not increased in size, 

 b. Head bearing numerous short, fine, secondary setae ; abdominal 

 segments 1 and 8 often bearing conspicuous dorsal cornicula. 



Melalophinae 

 bb. Head without secondary setae; dorsal cornicula never present. 



Pygaerixae 

 aa. Body bearing only primary setae above level of prolegs; anal pro- 

 legs usually elongated, 

 b. Dorsum of thorax consisting of a broad flattened triangle with 

 conspicuous lateral pro thoracic and mesal metathoracic angles; 

 anal prolegs long; head small, partially retractile. Cerurinae 



