6 



BlTLLETI]Sr 436, U. S. DEPARTMENT OP AGEICULTUEE. 



exceedingly limited numbers in the southwestern United States, but 



the farmer need not be concerned in regard to this, for the insects are 



quite similar in habits and methods of control. 



The adults of Chaetocnema ectypa (fig. 1) are 

 shining black, less than 2 miUimeters (three thirty- 

 seconds of an inch) in length, and nearly as broad 

 as long. Upon a corn leaf they appear as tiny, 

 nearly round objects, each about the size of the 

 point of a lead pencil. The species was origi- 

 nally described by Dr. George H. Horn in 1899. 

 His description is necessarily incomplete, since he 

 merely points out the difference existing between 

 Chaetocnema ectypa and Chaetocnema ohesula Lee, 



Fig. 2.-Tiie desert com which it vcry closcly resembles. The description 



flea-beetl'e: Egg. foUoWS: 



Greatly enlarged. 



(Original.) Surface distinctly aeneous. Antennae rufotestaceous at 



base, the five outer joints piceous. Thorax distinctly alutaceous. The punctation 

 extremely fine, indistinct, and sparse. The basal marginal line consists of fine, closely 

 placed punctures. Anterior and middle femora brown, the posterior femora piceous, 

 tibiae and tarsi rufotestaceous. Length, 0.06 inch; 1.5 mm. 



THE EGG. 



The eggs (fig. 2) are minute, averaging about 0.35 mm. long by 

 0.15 mm. m diameter, whitish and invisible to the unaided eye 

 unless placed upon a suitable dark or black background. They are 

 bean shaped, with one side slightly concave and one end smaller 

 than the other. The surface is sculptured and of a creamy white 

 luster, which becomes apparent when the egg is examined with a 

 binocular microscope. 



THE LARVA. 



The larvse (fig. 3) of this flea-beetle are elongate and quite small in 

 diameter; compared to the adult, they seem to be the young of a 

 larger insect. When 

 newly hatched they 

 are very small and deh- 

 cate, being less than 

 a millimeter in length ; 

 the measurements 

 of six specimens giv- 

 mg 0.80 mm., 0.75 

 mm., 0.70 mm., 0.75 

 mm., 0.80 mm., and 

 1.10 mm., they being eight times as long as their greatest diam- 

 eter. The head plate measures 0.1 mm. in width. They are pale 

 white excepting the head, which is a very fight straw color, and are 



Fig. 3. — The desert corn flea-beetle: Larva; o, anal segment, dorsal 

 view; 6, same, lateral view. Greatly enlarged. (Origiaal.) 



