In the female sternum of the eighth segment (fig. i, V^IIIStn) are the last of the series of ventral segmental plates. In the male the vent of the tenth segment is in the membranous dorsal wall of the genital chamber (fig. 24 A, X.V).
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS
10 SMITHSONIAN MISCELLANEOUS COLLECTIONS \0L. 94 with the metasternum in the notch between the sternellar lobes (SI 3)
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS II
THE ABDOMINAL SPIRACLES
12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 margin of the tympanal capsule just above the spiracle ; the long slender
THE TYMPANAL ORGANS
GRASSHOPPER ABDOMEN SNODGRASS
From the ventral end of the organ, the sensory nerve (Nv) continues to the large compound ganglion of the cord of the ventral nerve, which is in the metathorax. The tympanal organ of the Acrididae is usually regarded as a sound receptor, although little or no evidence of grasshopper hearing has been conducted.
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS IS
THE ABDOMINAL MUSCULATURE
The muscles of the body are well developed in the grass belly, especially in males, and individual muscles are easily distinguished. The series of numbers designating the abdominal muscles follows that of the thoracic Dissosteira (Smithsonian Misc.
MUSCLES OF THE FIRST SEGMENT
Several groups of muscles in the pregenital segments agree with the classification of the abdominal muscles into dorsal muscles, abdominal muscles, lateral muscles, transverse muscles, and spiral muscles, as given by the writer in a previous article (Ab-domen, Part I, Smithsonian Misc.
NO. 6 GRASSHOPPER ABDOMEN — SNODGRASS 17
MUSCLES OF THE SECOND SEGMENT
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 19 These muscles in the second segment are similar to those of the third
The sternopleural muscle of this second segment is a group of very short fibers (B,164) connecting the pleural sclerite with the sternum L. The dilator of the trachea {16^) is a long slender muscle which rises on the apodeme of the sternum, the occluder {166) is a short muscle, rising on the gum;.
MUSCLES OF THE THIRD SEGMENT
They take their origin on the posterior parts of the terga within the intersegmental folds, and are inserted on the overlapping front of the terga which follows in each case. In the posterior segments the corresponding muscles become much longer; the base of the median muscle migrated ventrally, that of the lateral muscle dorsal.
22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 are evidently torsion muscles, their transverse positions enabling them
6 LOCUST BELLY—SNODGRAS 23and goes dorsal to the insertion on the outside of the lateral apo- and goes dorsal to the insertion on the outside of the lateral apodeme of the sternum (fig. 10 B, lying). It is therefore a dilator of the abdomen and an inspiratory muscle in respiration, as its contraction separates the sternum from the tergum (fig. 11F, G).
MUSCLES OF THE EIGHTH SEGMENT
Muscles of spiracles.— The spiracular muscles are .. similar in segments II to VIII, and the description of those of the second spiracles will serve for each of the following spiracles.
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 25 internal lateral of the preceding segments, the first being absent in
MUSCLES OF THE NINTH SEGMENT
External lateral muscle (Fig. 12).—This muscle clearly corresponds to the first external lateral side of the pregenital segments. It arises on the anterior side of the ninth tergum and is inserted on the outside of the apodeme of the ninth thorax.
NO. 6 GRASSHOPPER ABDOMEN — SNODGRASS 29
MUSCLES OF THE TENTH SEGMENT
Dorsal dilator of the rectum.—A group of slender fibers arising dorsally on the tenth gum of other muscles (Fig. 14) fan out ventrally to their insertions laterodorsally on the posterior part of the rectum (Fig. 16A). Medianlevator cercusa (Fig. 7D.14).—Extrinsic muscle arising anteriorly on tenth tergum laterad of 287, inserted posteriorly on small sclerite between tenth tergum and basal. Ventral paraproct muscle (Fig. 14).—A broad muscle arising on the anterior margin of the lateral part of the tenth tergum, inserted posteriorly on the base paraproctventrally.
Transverse muscle (fig. 14). An unpaired, strap-like transverse muscle, present only in the female, lying dorsal to the base of the ovipositor and attached laterally to the tips of the tenth gums.
MUSCLES OF THE ELEVENTH SEGMENT
THE TRANSVERSE MUSCLES
THE DIAPHRAGMS AND THE DORSAL BLOOD VESSEL The so-called diaphragms of insects are transverse dorsal and ven-
Each of the slides. phragms differ much in the degree of development in different insects. Probably each diaphragm consists of a double peritoneal membrane, the layers of which are reflected by the walls of the body cavity; but the membranes enclose between them the dorsal and ventral transverse muscles, and the muscles become the main elements of the diaphragm. The dorsal diaphragm of Acrididae extends from the anterior end of the first abdominal segment to the posterior part of the ninth segment, and continues into the metathorax as narrow membranous ridges along each side of the aorta.
In the following segments, the borders of the dorsal diaphragm are difficult to define in a ventral dissection, except for muscle attachments for the lower one.
NO. 6 GRASSHOFTER ABDOMEN SNODGRASS 33 diaphragm membrane appears to be everywhere continuous with a
34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 anterior part of the thorax this diaphragm is merely a very delicate
THE PROCTODAEUM
NO. 6 GRASSHOPPER ABDOMEN — SNODGRASS 35 The circular muscles of the proctodaeum begin just behind the bases
The dorsal dilators (286) arise medially on the tergum of the tenth abdominal segment (Fig. 14), and their expanding fibers are inserted on the rectum along the lines of the latero-dorsal longitudinal muscles. The proctodaeal intimaline the Malpighian pockets and project to the edge of the overhanging fold. Between the alalpygial pockets, the wall of the proctodaeal pylorus forms 12 wide, pad-like thickenings (/?), which are crossed externally by the sphincter muscle (f), and which can therefore together form the pyloric sphincter apparatus between the stomach and the large intestine.
When the folds are accentuated by contraction of the proctodaeal muscles, they extend posteriorly through the colonorectum.
XO. 6 GRASSHOPPER ABDOMEN SNODGRASS 37 tapering or rounded at the ends, and having sharply defined margins
THE OVIPOSITOR AND ASSOCIATED STRUCTURES The ovipositor of the x\crididae is primarily a digging organ that
STRUCTURE OF THE OVIPOSITOR
38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94
The upper surface of the end lobe (B) is produced roughly as an elongated plate, orramus, at the end of which is a broad transverse depression that fits roughly into the visible protrusion from the lower surface of the basalramus of the corresponding third valve (D ,i). The lateral sclerite of the first valve basal valve (A,a) is the visible plate exposed on the ventral side behind the eighth sternum (fig. i). 94 of each dorsal valve is the strongly elongate anterior ventralramus (D,ra), the enlarged base of which (g) is strongly hinged on the dorsal edge of the exposed base (li) of the lateralapodeme of the same side.
The second or intermediate valves (Fig. 17A. B, D, 2]!) are short lobes projecting from the membrane between the ventral branches of the dorsal valves.
NO. 6 GRASSHOPPER ABDOMEN SXODGRASS 4I apodemes of the acridid ovipositor represent anterior apodemal proc-
The muscles which open the valves dorsoventrally consist of four large bundles of fibers which appear on the lateral apodemes, one pair dorsally (figs. 17A, B, 2yi), the other ventrally {2'/2). The closing of the valves is apparently done by the anterior intervalluval muscles, there are no muscles inserted into the valves that directly oppose the opening muscles. The only muscles that can serve as valve abductors are the retractor muscles located on the lateral basal ends of the third valves (fig. 17 C, 26^), which project laterally on the ninth gum.
The anterior intervalvular muscles consist of the median pair of slender muscles (fig. 17 C, D, 24'j') which originate anteriorly on the ninth sternum (fig. 13), and the lateral pair of broad muscles (^/j) arising on the inner margins of the basal parts. of the lateral apodemes; both pairs converge to their insertion on the small median apodeme of the anterior intervalvula.
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 43 are no tergal muscles in Acrididae corresponding with those inserted
IXTXT
The lateral apodemes of the ovary of Rhipipteryx are long shouldered plates projecting between the bases of the valves, but each. Walker describes the ovipositorapodemesof R.forcipata asshelf as extensions of the lower edges of the ninth tergum, having the same. FEMALE GENITALIA CH. SPERM AND SPERMATE OPENING The genital chamber, or conjunctive sac, of the female grass-.
THE FEMALE GENITAL CH.AMBER AND THE SPERMATHECAL OPENING The genital chamber, or copulatory pouch, of the female grass-
The anterior basal valvular sclerites of the first valves extend into their dorsal wall (Figs. 17 E, 20 A,C,c), and into a depression between the mallocated opening of the spermatheca (Spr). In Melanopliis the anterior end of the genital chamber is provided with two large lateral sacs (Fig. 20C,/), and the muscles {248), inserted on the basal vularenclerites (c) in Dissosteira, are attached in Melano-. In the Acrididae, however, it is very clearly an ingrowth between the eighth sternum and the base of the first gonopods, which are located behind the sternum.
The female gonopore in adult Acrididae, as mentioned above, is located on the floor of the genital chamber above the reflected posterior end of the eighth abdominal sternum.
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 47 the gonopore undergoes a posterior transposition that gives it its defi-
48 SMITHSONIAN MISCFXLANEOUS COLLECTIONS \0L. 94 groove of the body wall between the bases of the first valvulae (fig
DEVELOPMENT OF THE OVIPOSITOR
The best evidence for the origin of the ovipositor from limb structures is provided by the Thysanura. The valvulae of the ninth segment are not yet clear; the western region of this segment (IXS) shows no differentiation except two slight rounded swellings of its posterior margin. The two primary pairs of valvular processes increase in length with successive stages (fig. 21E), and the rudimentary second valvulae appear ventrally between the bases of the third valvulae (F, i'F/), but the relations of the valvulae to their respective segmental areas remain unchanged.
Updated stage, there is no evidence of the presence of valvifera, except for the small lateral sclerites (x) of the ninth segment, which increase in size and become more dorsal in position (F).
50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 In the last nymphal stage of the cricket, as illustrated in Gryllus
Between the bases of the second and third valve vulae of opposite sides are the small middle clerites which in adults become the interval vulae of the ninth segment. During the development of the ovipositor, it should be noted that there is a significant difference in the position of the parts derived from the two sexual segments. The first valvulae and the first valvifers develop from the ventral membrane of the eighth segment, completely posterior to the eighth sternum.
We may therefore assume that the apparent sternal region of the inth segment has acoxosternal composition, like the usual definitive sternal plates in the abdomen.
52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 virtually a part of the definitive first valvifer, by which the latter
The coxopodites of the ninth segment, in contrast, are apparently contained in the posterolateral parts of the apparent ninth sternum of the very young nymph (A, IXS); later they appear as separate. However, Nel (1929) took a different view of the matter, asserting that the manner and place of origin of the two first-formed pairs of ovipositor processes leave no doubt that the latter are serially ho-.
54 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 inologous, while the absence of median lobes between the processes of
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 55 The excavation of the egg cavity in the ground and the deposition
94Kiinckel d'Herculais says that the muscles play only a secondary role inKiinckel d'Herculais says that the muscles play only a secondary role in the expansion of the abdomen. It has also been suggested that the abdomen is distended by blood pressure created by a contraction of the thorax, but Grasse (1922) notes that there is no external evidence of any such contraction. The muscular equipment of the egg is therefore such that there is no need to invoke any other mechanism to account for the operation of the digging apparatus and the stretching of the stomach than that of the egg itself.
The eggs (from 10 to 14 in number) are almost always laid in the horizontal part of the next." Blatchley (1920) also records observations of the wood-burrowing habits of the same species.
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 59 the act of boring a hole in the upper edge of the topmost board of a
60 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 newly emerging egg is received between the closed valvulae, and he
GENERAL STRUCTURE OF THE MALE GENITALIA IN THE ACRIDOIDEA The terminal part of the abdomen of the adult male in both Acrididae and Tetrigidae is characterized by a large expansion of the ninth. The subgenital lobe of the ninth thorax is usually upturned at the end of the proximal plate, and its dorsal margin may be tightly closed against the lobes of the eleventh segment (Figs. 29 A, 30 A, 34A). However, due to the vertical position of the subgenital plate and the extension of the pallium forward of the latter, the opening of the cavity is dorsal between the eleventh segment and the bent edge of the pallium.
The floor of the chamber usually slopes posteriorly downward from the venter of the tenth segment (X.V) to the base of the inner pallial fold (Pal').
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 63 The phallic organs of the Acrididae consist of a complex of struc-
64 SMITHSONIAN MISCELLANEOUS COLLECTIONS \OL. 94 The lateral walls of the proximal part of the dorsal aedeagal lobe
Theaedeagus is usually completely hidden in the posterior part of the genital chamber under the hood of the pallium (Fig. The epiphallus itself is provided with a pair of large muscles (A, 26/) arising medially in the inner sternum, which curve upwards around the anterior end of the endophallus and the inside of the endophallus lobes (h) of the epiphallus Another pair of epiphallic muscles (B, 2/8) arises posteriorly on the zygoma of the aedeagal apodemes and extends anteriorly to the lateral lobes of the epiphallus.
The action of these muscles is not clear, but the muscles undoubtedly play a role in the function of the epiphallus in copulation.
68 SMITHSONIAN MISCELLANEOUS COLLECTIONS NOL. 94
Eppfc Papt
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 69 between the inner faces of the anterior apodemes of the lateral plates
70 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 94 by Walker (1922), they " are surprisingly unlike those of the Acridi-
NO. 6 GRASSHOPPER ABDOMEN — SNODGRASS 7I
COPULATION, AND INSEMINATION OF THE FEMALE Preliminary to copulation the male grasshopper places himself well
The removed tube remains for a long time in the calcaneum of the spermatozoa; the basal part of the spermatophore is soon rejected by the male. Spermatophores are formed at the beginning of the ejaculatory duct, but take their final shape only when they reach the end of the aedeagus. Here, the ends of the dorsal pair of sclerites are joined by a broad dorsal bridge (t), while the narrowed ends of the ventral sclerites are sharply bent upwards (s) and then gradually widen forward.
Thedorsal lobe of the aedeagus consists of a small proximal portion (C, ni) bearing two strong apodemal arms (Apa) and of four long curved apical processes (11, p).
78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 phallotreme, and in its inner walls are the usual phallotreme scleritcs
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 79 forward as a hoodlike fold that meets the lobes of the eleventh seg-
33 C, Gpr), with which the ejaculatory sac (fig. 25G, H, ejs) communicates with the spermatophoresis {sps) of the endophallus. The epiphallus is deeply sunk in the anterior part of the genital chamber, and the basal fold rises steeply towards the anterior surface of the aedeagus (C), hiding the basal parts of the latter. The endophallus is relatively small, but the anterior apodemes (iv) of its lateral plates are large and very distinct (E).
The primary part of the dorsal lobe is formed by the usual proximal subdivision (D, E, m), the distal part (E, r) is.
82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 very slender; those of the dorsal pair are united by an arched bridge
94Melanoplus mexicanus (Sauss.).– The general characteristics of this Melanoplus mexicanus (Sauss.).– The general characteristics of this species are sufficiently shown in Figure 38. The distal part of the dorsal lobe of theaedeagus is unusually long (D, E , r) and is produced in two terminal lobes laterad of the fallotreme gap. Connected to the base of each of these processes is a soft, flat accessory lobe (C, /) that lies on the dorsal surface of the base of the aedeagus.
The ventral processes arise, as appears to be characteristic of Melanoplus, deep within the phallotreme fissure (Fig. 41 B, p) and only their tips appear externally before the base of the dorsal processes (A, p).
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 85
88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 Grasse, p
NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 89 VOSSELER, J
