69] LEPIDOPTEROUS LARVAE — FR ACKER 69 



Antispila nyssaefoUella and Aspidiscus sp. (?). Head strongly 

 depressed ; front extending to vertical triangle ; two pairs of ocelli large 

 and conspicuous, the others reduced. Thoracic and abdominal legs want- 

 ing. Abdomen with kappa and eta distinctly separated but both on the 

 same swelling. 



Family Yponomeutidae 



Like the Pterophoridae this family is difficult to diagnose on ac- 

 count of the great variation among the different genera it includes. At 

 the same time there is little or no overlapping with other families. All 

 Yponomeutidae except Scythris and Schreckensteinia have beta below 

 the level of alpha on the prothorax, the Kappa group trisetose on the 

 prothorax, and kappa and eta distant on the abdomen. No other larvae 

 possess this combination of characters. The Tineoidea are the closest 

 and constitute the principal reason for introducing the alpha-beta char- 

 acter above. In view of this definite combination of setal characters and 

 the great variation in other particulars no general description is given 

 for the family. 



Schreckensteinia in the larval stage seems to be more closely related 

 to Gelechioidea than to Plutellinae, where the more recent authorities 

 place it. In addition to the characters given in the following table this 

 genus may be distinguished by the prolegs, which are long and slender 

 and at the tip bear from four to six crochets in a circle. 



The subfamilies may be separated as follows: 



a. Prolegs longer than wide ; crochets uniserial, either biordinal or uui- 

 ordinal ; Pi group on metathorax represented by a single seta. 



Plutellinae 

 aa. Prolegs wider than long ; crochets various. 



b. Body bearing numerous setae on verruca-like plates ; Pi group con- 

 sisting of four to eight setae on each abdominal segment. 



SCYTHRIDINAE 



bb. Body bearing primary setae only ; Pi group never bearing more 

 than two setae on thoracic or three on abdominal segments. 



Yponomeutinae 



Following are partial keys to the genera : 



Plutellinae 



a. Abdomen with kappa and eta remote, alpha and beta remote. 



b. Crochets arranged in a pseudocircle. Plutella 



bb. Crochets arranged in a mesoseries. Cerostoma 



aa. Abdomen with kappa and eta adjacent, alpha and beta adjacent. 



Schreckensteinia 



