124 
Psyche 
[March 
these different growth rates could be due to a variety of factors within 
the various host plant species. A particular host plant species may be 
deficient in certain nutrients necessary for proper larval growth and 
development or may contain various secondary chemicals which deter 
or inhibit larval feeding or physiologically interfere with the diges- 
tion, the assimilation and/or the utilization of food by the larvae. 
If the larvae reared on the wild umbellifer species gained less 
weight because of a behavioral deterence or inhibition of feeding, a 
reduction in the total food consumed or in the conusmption indices 
would be observed. However, all larvae on the 32 treatment groups 
ingested approximately the same total amount of food ( P < .3 ) , and 
consumed this food at approximately the same rate (P < .1) 
(Tables 2, 3). It thus appears that the observed reduction in growth 
rate was not due to a purely behavioral response to repellent sub- 
stances in the leaf material. 
Any physiological effect that would significantly reduce larval 
growth and development would become evident in either the reduced 
digestibility of the food or in a reduction of the efficiency of con- 
version of ingested food to larval biomass. In terms of the overall 
digestibility of the food, cultivated umbellifer species are significantly 
( P < 0.05 ) more digestible for the larvae than the weedy umbellifer 
species (Table 2). Along with this, the efficiency with which larvae 
utilize ingested matter for the production of biomass is significantly 
higher (P < 0.05) for larvae reared on cultivated umbellifer species 
(Table 2). It was also found that a strong correlation exists be- 
tween the dry weight gained per day by the larvae and the digesti- 
bility of the food (r = .586, 30 df.) and the efficiency of conversion 
of ingested matter (r = .711, 30 df.). It thus appears that some 
interference to the digestive processes is occurring in larvae reared 
on the weedy umbellifer species. This could be due to the action of 
secondary chemicals, either qualitative, quantitative, or both on the 
gut lining. This interference with digestion in the gut by the action 
of plant secondary chemicals has been previously established (Erick- 
son and Feeny 1973). 
Once the food material has passed through the gut, all larvae, be 
they reared on cultivated or wild umbellifers, utilize it for biomass 
production to the same degree (Table 3). A non-significant corre- 
lation exists between the efficiency of conversion of digested matter 
and the amount of weight gained per day (r = .248, 30 df.) and 
the efficiency of conversion of digested matter and the approximate 
digestibility (r = .258, 30 df.). This suggests that once the food is 
