Vergara - 1976 - Physiological and morphological adaptability of ri

EXPERIMENTAL APPROACH TO INSECT-CLIINIATE RELATTONSIHPS
Later. Bodenheiiner simplified his evaluative technique by assigning an index.
called a bonitation index. which reflected not only the number of generations per
year that could take place, but also the amount of reproduction. rates of survival
that could occur in each generation, and presence and nature of food supplies.
Again. the most favorable climatic habitats were those with the highest index.
And finally’. in still a further technique. Bodenheimer constructed climatographs
from the weather records of numerous places. and superimposed these on
temperature-humidity’ diagrams on which were drawn the developmental and
reproductive limits of the species. Favorable habitats for the fruit fly were judged
to be those places whose climatographs fell mainly utithin the temperature and
humidity limits; less favorable habitats were those that fell partly} within and
partly outside the phyisicwltvgical limits. and unfavorable places were those with
climatograplis that fell mostly outside the limits.
Perhaps the most comprehensive laboratory’ investigation inyrolving constant
temperature and humidity studies. followed by bioclimatic application to insect
distribution and abundance. is that of R. W. I-Iowe and colleagues at the Pest
Infestation Laboratory’. Slough, England. These studies concentrated mainly on
insect pests of stored grain products (rice. wheat. maize flour and meal). including
such pest species as the rice weexril. .S'iropiriliis orjtzae (L.) and the confused
flour beetle, Tribolimti confirszim DuVal (Howe. 1952. 1960). To oversimplify.
after finding the developmental. reproductive. and survival responses of the test
insect exposed to different constant temperatures and humiditics, they summarized
the results in the form of temperature-humidity diagrams. On these
diagrams. WhlCh for illustrative purposes we might call ecographs, were superimposed
climatographs of different places. much as had been done by Bodenheimer
in the case of the Mediterranean fruit fly. The combination of ecograph
and climatograph might then be called an ecoelimatograph.
On the ecograph. Howe and colleagues constructed limit lines for those conibinations
of temperature and humidity where complete development could just
take place. inside which areas the species could complete a life cycle and outside
of which it could not. Similar lines were located in respect to reproduction and
survival. Additionally. a series of lines was dravrn. more or less parallel. that
defined different rates of population increase. By simple superimposition of
climatographs. it is easily seen to what degree and for what parts of the year the
climate of a place is favorable or not for the species. Where climate is favorable.
rates of population increase could also be predicted.
CONSTANT VERSUS FLUCTUATING CONDITIONS
The use of constant temperatures to evaluate the responses of insects lo climate
has been criticized by many researchers, since for most terrestrial insect species
the thermal and hygral habitat fluctuates in 24-hour cycles (Messenger and
Flitters, I959). This was early pointed out by Uvarov (1931). who cited the works
of several investigators who detected differences in rates of insect development in
fluctuating conditions relative to what would have been predicted under the