22 MASS. EXPERIMENT STATION BULLETIN 261 



cent of the larvae in 80 per cent luiniidity, which were supplied with fresh 

 food, completed development. The food was near normal field conditions in 

 this case, although the water content of the leaves possibly may have been 

 slightly increased. The second series of larvae showed as rapid development 

 as the first, but the number maturing under these conditions was about 20 

 per cent less than with the third, indicating that the drying out of the food 

 between feedings may have been detrimental. The first series had the great- 

 est range of moisture environments. The detrimental influence of the drying 

 out of the food was very noticeable, the length of the feeding periods being 

 about 30 per cent longer and the percentage maturing greatly reduced when 

 compared with the results where the food was suitable. Probably the results 

 obtained in 32 per cent humidity were due largely to starvation rather than to 

 the dry atmosphere. A part of the data froni the larvae reared in 32 per 

 cent humidity was lost, but the estimated figures given in the table are very 

 close to the actual results obtained. A great majority of the adults reared 

 at this temperature were normal in size and appearance. 



Two different series of larvae were carried through the developmental cycle 

 at 22° (Table V, 22° Moisture Constant). The effects of moisture are shown 

 in the length of the growing periods, being several days less when the humid- 

 ity was high. A greater percentage of the larvae reached maturity in both 

 high and low moisture environn;ents. It is evident that a temperature of 22° 

 with humidity ranging from 40 to 90 per cent was favorable for larval de- 

 velopment. The adults reared in these environments were normal in appear- 

 ance, but those developing in the high humidity conditions averaged somewhat 

 larger in size than those which reached maturity in low moisture environ- 

 ments. This resvilt may have been produced by the better quality of the food 

 in the moist cabinets. Alternation of the larvae between the dry and wet 

 surroundings made very little change in the results (Table V, 22° Moisture 

 Varied). 



A temperature of 17° also was suitable for a large percentage of the larvae 

 reaching maturity, but about 40 per cent more time was required for them to 

 complete development (Table V, 17°). Only a few larvae were reared at this 

 temperature, but a check lot of fifteen larvae had nearly completed the feed- 

 ing stage when the experiment was closed, indicating that the results in the 

 table are normal. The adults obtained were large in size and normal in 

 appearance. 



The larvae reared in the 17° environments became quite dark in color. 

 During the feeding periods iiiost of the sjjines were gray or black in color, 

 but the body surface largely remained yellow. The pigmentation increased 

 with age and did not seem to be lost in molting. The cast skins appeared to 

 be clear and free from coloring matter. The pigment was retained by the 

 pupae, the greater part of the body surface appearing as gray or black in 

 color, but on transformation adults of the usual color pattern emerged. 

 Thomas (1924) observed the same effect when the larvae were reared during 

 the cooler part of the season. The black spots on the elytra of these beetles 

 apparently were not any larger than those on specimens reared at higher tem- 

 peratures. The accumulation of the pigment was probably caused by the low 

 metabolic rate of the larvae when reared at 17° which was not sufficient to 

 oxidize all of the melanin formed (Knight, 1924). 



Varied Envi(ronments. Larvae were reared under varied conditions of tem- 

 perature ranging from 17° to 32° and a moisture spread from 32 to 92 per 



