Response to cecropia cocoons of Mus musculus and two species of Peromyscus
SummaryIn rural areas cocoons of overwintering Hyalophora cecropia spum close to the ground are opened and the pupae eaten by small mammals, but in urban areas, where cecropia populations are much larger, the cocoons are almost never opened by mammals. Peromyscus leucopus noveboracensis and P. maniculatus bairdii are abundant in rural areas, but are largely replaced by Mus musculus in urban areas. In laboratory experiments P. l. noveboracensis invariably opened cecropia cocoons and ate the pupae. P. m. bairdii were slower to open cecropia cocoons and two of twelve did not open one at all. M. musculus, on the other hand, never opened cecropia cocoons although they gnawed the silk and ate uncovered pupae. Cocoons opened in the laboratory by the two species of Peromyscus cannot be distinguished from each other or from cocoons opened in the field.
Natural Materials and Products from Insects: Chemistry and Applications
Lac is a natural resin secreted by Indian lac insect, Kerria lacca (Kerr), which thrives on the tender twigs of specific host trees. Lac is collected as the minor forest produce and cultivated since time immemorial in India, and lac cultivation is an important source of income for livelihood of the forest and sub-forest dwellers of central and eastern India. Lac still enjoys the monopoly of non-toxic, biodegradable, natural and safe resin and used for applications in pharmaceuticals, cosmetics and surface coatings for variety of uses in industries. India is the largest producer, processor and exporter of the lac, having average production of 20, 000 tons for the last 5 years. Organized research on lac was started in India after realization of its commercial potential worldwide. Research as well as documentation on all aspects of production, processing, product development and use diversification of lac has led to generation of authentic information. During processing of lac, various economically important by-products are obtained. The major component of lac is resin (65%) followed by two important by-products, viz. lac dye (1%) and lac wax (5–6%). The lac resin is processed into various value-added forms as per the need of the different industrial applications. Similarly, the dye and wax find its application in various sectors such as pharmaceutical, textile, etc. This chapter covers processing, chemistry of lac and its by-products and industrial and other applications, and also on outlining the future scope of the work.
THE SELECTION INDEX AND ITS TEST OF SIGNIFICANCE
Under experimental conditions in which equal numbers of individual animals of two types, A and B, are exposed to selection by a predator with the result that the numbers of individuals taken are a and b and the numbers not taken are c and d, respectively, making a combined total of n, then we may measure the strength of selection by the selection index: (a b)/(a + b). Should a greater number of type A than of type B individuals be taken (selection against A), then the selection index will be positive, while if more of B than of A are taken (selection against B), the index will be negative. The formula which I earlier proposed (Dice, 1947: 3) for the calculation of the chi-square of the difference between the numbers of A and of B taken under such conditions, unfortunately, is inappropriate. This has been pointed out to me by Don W. Hayne, who also has given other aid with this problem. The formula for chi-square earlier given, (a-b)2/(a+ b), is correct for a 1:1 ratio, as stated, but that formula takes account only of the successes in each of the two classes and neglects the failures in the same classes. The chi-square appropriate for testing the significance of the deviation index from zero is that for a 2 x 2 table: