24 MASS. EXPERIMENT STATION BULLETIN 189. 



Oats. 



The stalks of volunteer oats were found infested by the larger larvae 

 of the borer in one instance. The injury and its results were similar to 

 that described for other plants with a like habit of growth (pigweed, etc.). 

 Only a very small percentage of oat stalks present wa;S infested. 



Oats may become important economically as a food plant of the borer 

 because of the fact that oat straw is often used as packing material. 



Turnij)s. 

 Large larvae of the European corn borer were observ^ed feeding upon 

 the outside surface of the tender leaf stems of the turnip. They were 

 not found within the turnip plants, and it is believed that this plant is 

 not at all important as a host of the borer. 



DESCRIPTIONS OF THE DIFFERENT STAGES. 

 The Egg. 



Average length, .97 millimeter; average width, .74 millimeter; circu- 

 lar ovate in shape, slightly convex on its upper surface, flat on its lower 

 surface, or conforming to the shape of the object on which it is deposited. 

 Exochorion sculptured with shallow pentagonal or polygonal pits. Endo- 

 chorion apparently smooth. Color, when first deposited, opaque white, 

 often strongly iridescent. In from eighteen to twenty-four hours after 

 deposition a crescentiform clear space is formed in the center of the egg 

 on its upper surface. About two days before hatching the egg assumes 

 a yellowish tinge, and soon thereafter the developing larva becomes 

 visible and imparts to the egg a yellow-black appearance. 



The eggs are commonly deposited in irregular-shaped masses, each egg 

 overlapped by the adjacent ones m the manner of shingles. Each egg 

 mass is composed of from 5 to 50 eggs. 



The Larva. 



First Instar (see Plate I, Fig. 1). — Average measurements of 11 indi- 

 viduals, newly hatched. Length, 1.6 millimeters; head width, .30 

 millimeter. Length of head and prothoracic shield, one-fourth total 

 length of larva. Bodj^ subcylindrical, opaque white to yellowish green 

 in color. Tubercles large, prominent, pale amber gray. Primary setae 

 long, amber-colored. Anterior stigmatal tubercle on prothorax bisetose, 

 the upper seta the shorter; sub ventral tubercle also bisetose, the anterior 

 seta the shorter. Tubercles and setae iv and v are absent on meso- 

 thorax and metathorax; coalescent on abdominal segments 1 to 8, inclu- 

 sive; situated below the spiracle on segments 1 to 7; below and slightly 

 anterior to spiracle on segment 8. Tubercles ia-i6 and iio-ii6 coalescent 

 on meso thorax and metathorax. Setae ia and iia are shorter than setae 



