6 AIASS. EXPERIMENT STATION BULLETIN 375 



was about 30 days at 80° F. and about 40 days at 70° F. In these studies 

 no regular and consistent development at 60° F. was observed, but records 

 indicate that the retarding influence of this temperature might extend the 

 life cycle to 105 days. When the larvae were fed only mealybug eggs — 

 which appears to be a deficient diet, although the insects were normal — 

 the life cycle was extended to 54-56 days at 80° F. and to 68-72 days at 

 70° F. It is probable that any unfavorable conditions which are not fatal 

 may extend the life cycle in much the same way that low temperature did. 



Oviposition 



In the Greenhouse. In 1933 and 1935, beetles which had been received by 

 air mail from California were paired and confined in jelly glasses in a 

 greenhouse compartment. This compartment was used for various pur- 

 poses, and the temperature during the winter when the observations were 

 made varied from 40° to 75° F. without any regular control. The beetles 

 were supplied with clusters of mealybugs, usually including a quantity of 

 eggs. Under these conditions the beetles lived from two to three months 

 and laid eggs on 15 to 20 percent of the days. 



In 1933, female beetles laid an average of 55.6 eggs during their life, and 

 one laid 107 eggs. On three different days 11 or 12 eggs were laid by 

 one beetle, but the average number of eggs per beetle per day on days 

 when eggs were laid was 3.09. 



In 1935, when the beetles were kept in the same greenhouse but under 

 less favorable conditions, the average number of eggs per female beetle 

 was 11.4 and the beetles died about a month earlier than in 1933. 



In Constant-Temperature Cabinets. In 1935 and 1937, oviposition records 

 were secured at constant temperatures, using mated pairs of beetles con- 

 fined in jelly glasses with moist sand in the bottom. Mealybug egg 

 masses on gardenia leaves furnished favorable conditions for oviposition 

 and records were taken daily. The temperature cabinets were not equipped 

 with liumidity control and no attempt was made to provide moisture in 

 1935. In 1937, however, basins of water were placed in the cabinets and 

 these supplied a moderate but variable humidity ranging from 40 to 60 

 percent. 



From Table 1, it is evident that the conditions in 1937 were much more 

 favorable for the beetles than they were in 1935, and the number of 

 eggs laid in these two experiments may be considered as representative 

 of this activity during unfavorable and favorable conditions. Smith and 

 Armitage (16) state that 25 beetles (sex not given) produced in breeding 

 trays 400 to 1,000 adults, which would equal an increase of 16 to 40 per 

 beetle; ])ut that the beetles were confined with their host only 18 days, 

 wliicli represents only one-fourth to one-half of their oviposition period. 

 Furthermore, these figures do not take into consideration the mortalitj- 

 from accidents, cannil^alism, or other natural causes. Observations in 

 greenhouses where liberations were made have shown an estimated increase 

 in one generation of 6 to 10 per beetle or 12 to 20 per female beetle. 



It is also evident in Table 1 that oviposition is decreased at temperatures 

 below 80° F., and that the number of eggs laid at 60° F. is only al)nut 

 one-third the number laid at 80° F. 



