University of Massachusetts Amherst ScholarWorks@UMass Amherst Doctoral Dissertations 1896 - February 2014 1-1-1931 The pleural and sternal sclerites of the lepidopterous thorax: A contribution to the revision of the genus Pyrgus in America (Lepidoptera, Hesperidae). The effect of hydrogen ion concentration upon the toxicity of nicotine, pyridine, and methylpyrrolidine to mosquito larvae. Harold Henry Shepard University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/dissertations_1 Recommended Citation Shepard, Harold Henry, "The pleural and sternal sclerites of the lepidopterous thorax: A contribution to the revision of the genus Pyrgus in America (Lepidoptera, Hesperidae). The effect of hydrogen ion concentration upon the toxicity of nicotine, pyridine, and methylpyrrolidine to mosquito larvae." (1931). Doctoral Dissertations 1896 - February 2014. 897. https://scholarworks.umass.edu/dissertations_1/897 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Doctoral Dissertations 1896 - February 2014 by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. 312Qbb Paid 3711 1 The Pleural and Sternal Sclerites of the Lepidopterous Thorax, Etc, Harold H. Shepard THE PLEURAL AND STERNAL SCLERITES OF THE LEPIDOPTEROUS THORAX A CONTRIBUTION TO THE REVISION OF THE GENUS PYRGUS IN AMERICA (LEPIDOPTERA, HESPERIDAE) THE EFFECT OF HYDROGEN ION CONCENTRATION UPON THE TOXICITY OF NICOTINE, PYRIDINE, AND METHYLPYRROLI DI NE TO MOSQUITO LARVAE. (With Charles H. Richardson) By Harold H. Shepard Thesis submitted in partial fulfillment for the degree of Doctor of Philosophy, Massachusetts State College. Amherst, Massachusetts May 1931. THE PLEURAL kWD ST15RTTAL BCLERITES OF THE LEIIBOPTEROUS THOPAX By Harold H.Shepard Appearing in Annals Entomological Society of America for June, 19.30 THIS PLEURAL AND STERNAL SCLERITES OF THE LE^IDOPTKROUS THORAX.* Ey Harold H. Shepard,U. P. Bureau of Entomology, Washington, D. C. INTRODUCTION Some excellent studies have been made by various workers on the morphology of the sclerites of the thorax of insects. Few of these, however, have dealt with the thoracic sclerites of Lepidoptera. Many of the figures of the thorax of Lepidoptera that may be found in our ^resent literature are either very unsatisfactory drawings ar are merely included in a general study of all orders of insects with respect to the morphology of this body- region. No American investigator up to now has devoted much study to the different types of development in the lepidopt erous thorax.' *This paper is offered as a thesis in partial fulfil- ment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Agricultural College. The author is indebted to Dr. G. C. Crampton for his suggestion of the subject and for his helpful interest and encouragement, and to Dr.H. T. Fernald for his kind assistance in 'Securing srecimens from various sources. He also wishes to express his appreciation of much useful criticism b</ Mr . R. E. Snodgras s of the U.S.Buraau of Entomology. Because of the evident value of a study of the thoracic sclerites in determining the phylogenetic relationships of the families of insects, this study has been undertaken. In the Lepidoptera there is a somewhat customary linear arrangement of families. When any attempt has been made to derive a phylogenetic tree to show which families are the more primitive and generalized, and which the more specialized, and to show how close the more primitive families may be to the ancient lines of development of which the higher families are the result, there has be=n considerable disagreement amongst the various arrangements which have been published. A discussion of phylo- geny, it seems to the author, should be based upon a careful comparison <ff many species in each family, in order that there may be no conclusion based upon aberrant forms. Owing to a great lack of information only a few general conclusions con- cerning phylogenetic relations in the Lepidoptera may be pointed out at this time. At a,later date it is hoped that further study will have-gained for us sufficient material to formulate, in conjunction with play log•attic evidence from the other useful characters, a general family relationship in the Lepidoptera. GENERAL TERMINOLOGY In this discussion two forms will be employed for illustration, namely, Mellttia satyriniformie Hbn. (Aegeriidae) (Fig.l) ana Gatocala concumbeng wik. (Noctuidae) (Fig. 3). It is not claimed that the former species is particularly primitive in many respects. The species is used here because it shows in the one insect 'most features of the pleural region which occur in part in many of the higher families of Lepidopteraj Catocal a concumbens is representative of the latter. The figure in the text may be referred to for the general relation- ships of the various features of the lepidopterous i.ieso- leuron and sternum. The terminology used is that adopted by most of the recent writers on general morphology of the thorax, such as Crampton (1S09l-1S36), Snodgraa^ (1537), Young (1931), etc. I dowever, certain characteristic sutures and other formations not previously named in the lepidopterous thorax require descriptive terms bv which they may be designateu in such a paper as this one. j 4 Diagrammatic Structure of t s e Typical lepidopterous Mf«opleuron and Sternum. basicostal suture a, anep-i sternal suture; aes , anepisternum; be, ec_, euccxa; epimeronj os , basisternite; c_, pleural suture; fm, fs_, suture; ea , tpiiterniamj furcisternite; g_, maxglnoplrural h, .-iiaventral suture: .m, weron; i; e:.:$ preepi.-.eronj ,:sa / pree.. i sternum; sa, subalare; si, sternal Itobe; spinisternite; vr, preepisternal suture; vvp_, pleural wing proeesBj x> epicoxal piece; precoxal suture; y, ~~z, anepiat trna^ sutural connective. ' 5 Each typical wing-bearing segment in the Lepidoptera has a pleural suture (c) (see text figure), traversing the pleural region from the pleural wing process (wp_) to the ©oxa. The part of the pleuron anterior to the suture and which "always extends from the top to the bottom of the pleural plate" (Crampton,lS14a) , is called the epi sternum (es) while that posterior to it is the epimeron (em). Quoting from Young (1321), "The straightness of the pleural and coxal ridges is a mark of pri.nitiveness. " While this is a general truth in the case of the pleural suture, it is not strictly so in the two species figured for illustration of these terms. The aegeriid Mel-it tia satyriniformis (Fi?,l) has the pleural suture (or 'ridge') extremely curved, while Catocala concumbens (fig. 3)j in a family considered to be more highly developed in general than the Aegeriidae, has a pleural suture less curved. However, M. satyriniformis -.ay be considered a member <ff a lower family which has particularly developed so as to bend the pleural ridge out of proportion to the rest of its development/ . In this order the basicoxite is enlarged by the distal extension of th^ basi co stal suture (bcft on the coxa posteriorly to form the large meron (m), as is the case in the Neuroptera, Mecoptera, TricJieptera, some Diptera, etc. Snodgrass (132?) figures the coxa of Conopia ( Aegeria ) exitiosa Say and discusses . the relationships of the basicoxite. Insuch families as the Micropterygidae (Fig. 5), Hepialidae (Fig. 8), Megalopygidae (Fig. Pyromorphidae (Fig. 9), 18), and Psychidae (Fig. 16) there is none of the anterior part of the basicoxite visible extern In Adela purpura Wlk. (Fig. 8^ and in most of the higher famil there is in the angle of the euooxa between the mercn and the Tleuron a small sclerite which may be called the epicoxal pie, (x); it is undoubtedly the exposed part of the basicoxite anterior to the pleural articulation of the coxa. A t opical subdivision of the mesothoracic •pisternum occurs in the Lepidoptera. A longitudinal suture cute the epi sternum of this segment in nearly equal parte, the Tapper smaller one being the anepi sternum (aes), and the lower the kat epi sternum. The katepisternum is fused to such an extent with the sternal regions and then so divided by secondarv sutures that other terms have been found more useful in such orders as the Neuroptera, Mecoptera, Trichop$era, Lepidoptera, etc. The lower region of the episternum together with the sternum is termed the st ernopleurite ( spl ) A process is found in many of the more highly developed Lepidoptera, »uch as the Hlyphipterygidae, Aegeriidae, Georaet- ridae, Noctuidae, Sphingidae, Saturniidae, etc., which may be called the stern al lobe (s_l) (see text figured, and ia an anterior projection of the lo-?er region of the episternum which overhangs the sternum. It is sometimes verv prffiminent and covers a considerable pocket which extends entirely across the sternal region. 7 Ths an epl sternal suture ( aes ) is a verv useful landmark. In a very few cases, such as Thyris maculata, has it been found lacking. It is usually present as a membranous o-oen cleft (Episternalsp_all, Weber, 1928), extending from the anterior margin of ths episternum about three-quarters of the distance to tne pleural suture. Sometimes itb is closea, the opposite of margins the cleft being drawn together. Sometimes it extends entirely to the pleural suture, but usually the posterior -art is onjky slightly visible as an internal thickening of the exoskeleton. Usually whan a connection with the pleural suture is visible, there is a tendency, especially in the higher families, for the anepisternal sutural connect ive (z) to migrate down that 3uture. In M. satyriniformi the anepisternal sutural connective has migrated to the lower end of the pleural suture. In Corydalis cornuta L. (Meuroptera) (Fig. 3) there is a secondary suture extending from the posterior end of the anepisternal suture direct iy to the midventral suture cutting the sternum into basistern ite (bs ) anteriorly and furcisternite (f_s) posteriorly.