Document Type

Thesis - Open Access

Award Date

1934

Degree Name

Master of Science (MS)

Department

Entomology-Zoology

Abstract

The most destructive grasshoppers that occur in South Dakota are those belonging to the genus Melanoplus. Of those, the common and harmful species are Melanoplus bivittatus (Say) and Melanoplus differentialis (Thomas). Other species that are of considerable economic importance, and, at times, fully as important as the two species mentioned, are Melanoplus femur-rubrum (Deg.) and Melanoplus mexicanus (Sauss.). Before attempting to work out a plan for grasshopper control, it is desirable at times to know what species are to be encountered. The control may vary to some extent for the different species. It has been found that Melanoplus differentialis hatches about two to three weeks later than Melanoplus bivittatus. Therefore it is important, at times to know what species are predominant in an area. It seems that a method of identifying the eggs of the common grasshoppers would be desirable. So far, there has been but littlr work done on this phase of grasshopper study. The writer was unable to find any literature which gave a key for identifying the eggs of the common species of grasshoppers. Many writers recognized that the eggs of the common grasshoppers differed in appearance (4) but they offered no name identifying the eggs of any one species. The description of grasshopper eggs were so general that they could be applied to almost any species. The writer has studied the eggs of eighteen species of grasshoppers representing ten genera and four subfamilies. Not all of those species are of economic importance, but all of them are important from a taxonomical viewpoint. The classification of grasshoppers is based on external rather than internal structure. Modifications of certain external structures have been used in the grouping of our grasshoppers. Morphologist generally agree that differences in the internal reproductive system are the more primitive and are more useful in showing broad categories. From the discussion on page 10 , it can be seen that the pattern of chorion of the eggs is also a study of the morphology of a portion of the ovarian follicle. If we find a different relation between species when studying the evolution of the various reproductive systems than is expended by the characters now used in our system of taxonomy, it is evident that the present system is an unreliable one. Furthermore, there is , at present , a disagreement between orthopterists as to how various species should be grouped. As is evidenced by this disagreement, the characters now used are not satisfactory. The writer hopes that his studies which show variations between the eggs of every species will be of some value in indicating how these problems may be solved.

Library of Congress Subject Headings

Grasshoppers -- Eggs
Locusts -- South Dakota -- Eggs
Melanoplus bilituratus
Melanoplus differentialis

Description

Includes bibliographical references (page 25)

Format

application/pdf

Number of Pages

36

Publisher

South Dakota State University

Included in

Entomology Commons

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