10 BULLETIN 967, U. S. DEPARTMENT OF AGRICULTURE. 



LIFE HISTORY AND HABITS. 

 MACROBASIS IMMACULATA Say. 



Oviposition. 



The female of Macrobasis immaculata deposits her eggs in small 

 cavities (fig. 10) prepared in the soil wherever she may be feeding. 

 In confinement no special preparation or arrangement could be ob- 

 served. While on the staff of the Kansas Experiment Station the 

 writer once observed oviposition in the field. The ovipositing female 

 first came under observation about 3.30 p. m. She was busily engaged 

 in excavating and continued thus as long as watched. The place Avas 

 marked, and the writer returned at 6 o'clock to find her still at work. 

 The next forenoon the spot where the beetle had worked had been 



smoothed over, nothing remaining to indi- 

 cate the location of the eggs except the 

 identifying marks. Careful excavation re- 

 vealed the outlines of a bell-shaped cavity 

 in which the dirt had been replaced and 

 FlG . io.— cavity prepared for loosely packed. In the center of the floor 

 eggs by female of Macrobasis was a smaller cavity that contained a mass 



immaculata. „ , -, -, -, rp-i 



of several hundred eggs, lne eggs were 

 about 1| inches below the surface, and without definite arrangement 

 or protective covering. 



The earliest date at which eggs were secured in confinement was 

 July 22 and the latest September 9. 



Incubation. 



As incubation ( proceeds the young larva soon becomes visible 

 through the transparent shell. The body is translucent, distinctly 

 segmented, and the head is closely appressed on the venter. The 

 mouth parts extend backward below. The eyes are black, the tips 

 of appendages brown, and the spiracles are ringed with brown. The 

 hairs are closely pressed to the body, the two long ones on the anal 

 segment being bent around so as to extend forward at the sides. 



Eggs deposited July 22 hatched August 3, and some deposited 

 July 24 hatched on August 5 and 6. The incubation period is thus 

 from 12 to 14 days in length, but this becomes increased during 

 cooler weather. 



Habits and Growth of Larva. 



The newly hatched larva soon becomes active. Where the beetles 

 are numerous during the summer the little triungulins soon abound, 

 and close observation will discover them hurrying about over the 

 ground. They go into every crevice and under every clod and piece 



