NORTH AMERICAN ACROLOPHIDAE — ^HASBROUCK 503 



of certain species. Normally, the genitalia of the male are partially 

 extruded from the tip of the abdomen. 



The male genitalia are of a primitive type similar to those of the 

 Tineidae. The uncus may terminate in a single process, it may be a 

 strongly bifurcated organ, or it may represent any one of a fairly 

 complete series of transitional forms between these two extreme con- 

 ditions. Likewise, the incomplete gnathos may be paired or fused, 

 with a series of intermediate forms. The harpes are large and com- 

 monly spoon-shaped. The cucullus of the harpe rarely bears a 

 clasper, while the costa bears a large, dorsal process in several species. 

 The transtilla is incomplete, consisting simply of a pair of slender arms 

 attached to the harpes. The aedeagus is rather large and normally 

 somewhat expanded or bulblike at the base. It has a large, eversible 

 vesica which commonly bears one to many cornuti. The anellus 

 is typically membranous and unarmed. Rarely, it is partially scler- 

 otized or furnished with minute, spinelike processes. The juxta 

 is normally absent, although it is present in a rudimentary or reduced 

 form in a few species. The vinculum is a simple, U-shaped pouch 

 serving as a base of attachment for the various genital organs. The 

 major genital structures commonl}^ occurring in other groups of 

 Lepidoptera but lacking in the Acrolophidae are the paired socii, 

 the saccus of the vinculum, the clasper of the harpe, the central 

 bridge of the transtilla, the median ventral plate of the gnathos, and 

 the juxta or medioventral plate of the anellus. 



The larva, called the "burrowing web-worm," has been charac- 

 terized by Forbes (1923, p. 119) as follows: 



Larva with front reaching only halfway to vertex, the adfrontals very wide 

 and reaching vertex; ocelli six, but not regularly arranged, the fourth and lower 

 being much closer together than the second and third are; head ventrally chi- 

 tinized behind labium. Leg with trochanter one-third as wide as femur; pro- 

 thoracic legs separated by a distinct, chitinized sternum; thorax with setae on 

 large shields; tubercles iii to v apparently taking the place of pleural sclerites; 

 cervical shield extending the whole width of the prothorax and enclosing the 

 spiracle; prolegs with one complete ellipse of hooks, preceded by several (3-6) 

 rows of rudimentary ones; the anal proleg with a curved band. 



The larval habits of several species occurring in Illinois have been 

 described by Comstock (1924, p. 611). His description, partially 

 drawn from the observations of Forbes (1905), is as follows: 



The larvae normally live in the ground feeding on the roots of grass. Each 

 larva makes a tubular web opening at the surface and leading down into a ver- 

 tical C3-Iindrical burrow about the diameter of a lead-pencil, and six inches to 

 two feet, or even more in depth. The larva measures about 25 mm. in length. 

 Sometimes the larvae injure young corn when planted on sod. They surround 

 the base of each plant with a fine web mixed with earth and pellets, building 

 this up in the lower blades, which they slowly eat away. As they get larger 

 they eat the stripped plant to the ground. When disturbed they retreat into 

 their web-lined burrows. 

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