February, '17] COOLEY: SPINACH CARRION BEETLE 99 



As they increased in size the eggs tended to become more nearly spheri- 

 cal though they were plump and smooth when laid. The increase in 

 size was much more rapid soon after being laid while shortly before 

 hatching there was practically no increase. 



It was assumed that the increase was due to the absorption of moist- 

 ure by osmosis. 



Incubation Period 



Thirty-eight exact incubation records were made in the insectary in 

 1915. The maximum period was 6 days, the minimum 3 days and 

 the average 4.76 days. 



The Larval Period 



From hatching to the pupal condition the insect molts three times. 

 Exact records of the stadia have been made, as follows: first stadium, 

 maximum 8 days, minimum 4 days, average of 25 records, 5.08 days; 

 second stadium, maximum 7 days, minimum 4 days, average of 10 

 complete records, 5 days; third stadium, maximum 18 days, minimum 

 12 days, average of 9 complete records, 14.66 days. 



Habits of the Larv^ 



The black larva? are rather conspicuous objects against the green 

 leaves of the young sugar beet plants in the field. They are easily 

 disturbed and when frightened tumble to the ground and crawl rapidly 

 to cover under clods of soil. Much of the time is spent hidden beneath 

 the surface. The larvae like the adults are adapted to a variety of 

 food plants and their presence in a sugar beet field indicates that some 

 one or more of the favorite plants is in the neighborhood. The beet 

 crop probably is not generally responsible for the presence of the 

 insects in considerable numbers in a given locality. In some instances 

 that have come under our notice the larvae became troublesome in 

 beet fields only after their weed hosts had been defoliated. 



The larvae prefer to feed during the night and remain in hiding in 

 the soil during the day, but when thej^ are abundant in a field some 

 may be found during the day. Both the adults and the larvae feed 

 from the edges of the leaves and injured plants present a characteristic 

 appearance. The mandibles appear to be poorly adapted to make 

 clean cuts in removing bits of the foliage and the edge of a gnawed 

 leaf often shows a thin projection of crushed tissue. 



When fully grown the larva burrows into the soil to a depth of one 

 to two inches and constructs an oval cell in which to pupate. 



Duration of Pupa Stage 

 All individuals forced to pupate in tin cans with insufficient earth 



