The Affinities of Grylloblatta indicated by a Study of the Head and its Appendages.
Psyche 33(3):78-85, 1926.
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78 Psyche - [June
THE AFFINITIES OF GRYLLOBLATTA INDICATED BY A STUDY OF THE HEAD AND ITS AP-
Massachusetts Agricultural College, Amherst, Mass. Since specimens of Grylloblatta are extremely rare and valuable, I am deeply indebted to Mr. Eric Hearle and to Mr. H. S. Barber, for their kindness in supplying me with the material used in the preparation of this paper. The following discussion is based upon the study of Grylloblatta carnpodeiformis Walk., and Grylloblatta barberi Caud., with which I have been able to compare sketches of the parts of the only other known Gryllo- blattid, Galloisiana nipponensis Caud., through the kindness of Mr. A. 'N. Caudell.
The affinities of Grylloblatta indicated by the study of its terminal abdominal structures have been discussed by Walker 1919 and 1922; and the writer (Crampton 1915, 1917, 1923, 1924 and 1926) has discussed the evidence of its affinities in- dicated by a study of its antenna, maxillae, head, thorax and ovipositor. I believe that Grylloblatta is practically a living Protorthopteron very closely related to the common stock from which sprang the Tettigonioid and Grylloid Orthoptera, and the closest affinities of Grylloblatta are with the Tettigonioids. Outside of the true Orthoptera, the next of kin of the Gryllo- blattids are the Dermaptera, and the Phasmids are somewhat more remotely related to them. The Grylloblattids (with the rest of the Orthoptera) Dermaptera and Phasmids were descended from a common Protorthopteroid stock which also gave rise to the Embiids, whose line of descent parallels that of the Gryllo- blattids rather closely, but the nearest relatives of the Emblids are the Plecoptera. The Protorthopteroid ancestors of. the Or- thoptera (including Grylloblatta) Dermaptera and Phasmids were descended from Protoblattoid forms, from which the Blattids and Isoptera have departed but little. In the following Pu&e 33:77-84 (1926). hup ttpsychu einclub orgt13/33-077.htd
19261 The Affinities of Grylloblatta 79
discussion I would point out the evidences for this view afforded by a study of the head and its appendages in Grylloblatta. The head capsule of Grylloblatta as shown in Fig. 2, gives no support to the view of Imms, 1925, for example, who maintains that Grylloblatta is one of the Cursoria, since the head of Gryllo- blatta is very similar to that of the Orthopteron Gryllotalpa in its-general outline, the position of the eyes the 'ocation of the antennae, and numerous other features. Gryllotalpa, however, and the other Grylloid Orthoptera have ocelli, so that in acking these structures, the head of Gryllobzatta resembles that of certa'n Tettigonioid Orthoptera such as Ceuthophilus, as is also true of other features of the head in these insect . On the other hand, the head of Grylloblatta is not like that of such Cursoria as the Blattids, Mantids, etc.. and the evidence from this sou ce would indicate that Grylloblatta is either a true Orthopteron, or possibly a relict of he extinct Protorthoptera-like ancestors o" the Gryllo~ds and Tettigonioids.
In tracing the type of head capsule exhibited by the Gryllo- blattids to its prototypes in the lower Orthopteroids clustered about the base of the line of descent of the Orthoptera, it at once becomes evident that the head capsule of Grylloblatta is so like that of the Dermaptera that the head of Grylloblatta should be referred to as Dermapteroid or Forficuloid. Thus, in a typical Dermapteran head, there is a pale anteclypeus, like the region labelled ac in Fig. 2; the antennae are located near the bases of the mandibles, as in Fig. 2; the eyes are located far down the tempora (tm of Fig. 2); temporal sutures (ts of Fig. 2) demark the temporal regions tm from the parietal regions pa; the arms of the frontal suture fs are widespread as in Fig. 2; there are no ocel'.i present, and many other features of the Dermapteran head- capsule clear'y indicate that the head of Grylloblatta (Fig. 2) is Dermapteroid. The evidence of the head-capsule would thus indicate that among the lower Orthopteroids, the Dermaptera are the next of kin of the Grylloblattids, and the correctness of this view is borne out by the evidence of the thoracic sclerites and many other features.
The head capsul of the Phasmids such as Timema approcah- es the Grylloblattid and Dermapteran type in most of the features
80 Psyche [June
mentioned above, but the Phasmid type although clearly derived from the same source, apparently follows a path of specialization leading to extreme development along the l'ne of massing the parts in the anterior region of the head, thus leading away from the common ancestral type from which the Grylloblattids and Dermaptera arose. The relation of the eyes and antennae, etc., to the bases of the mandibles is likewise very similar in the Em- biids and the forms mentioned above; but the Embiid type is evidently leading away from these Orthopteroids-although it, also, was evidently derived from Protorthopteroid prototypes. The study of the head capsule thus bears out the evidence from other sources indicating that the Grylloblattids, Dermap- tera and Phasmids are closely related, and sprang from a common Protorthopteroid ancestry; and these in turn were evidently derived from Protoblattoid ancestors. The Blattids, Mantids and Isoptera are the nearest living representatives of these Protoblattoid ancestors, and of these the Isoptera are in some respects the nearest living representatives of the Protoblattoid forms giving rise to the Protorthopteroid ancestors of the Gryllo- blattids, Dermaptera and Phasmids, so that we would expect to find among the Isoptera some types of head capsule suggesting the prototypes of the Dermapteroid head characteristic of the Grylloblattids, Dermaptera and Phasmids, and such is indeed the case. The resemblance, however, is more striking when one compares a Grylloid head, rather than the Grylloblattoid type, with a typical Isopterous head, since the head-contour, relation of the eyes, antennae, bases of the mandibles, etc., are more nearly alike in the Grylloids and Isoptera, than is the case in the Grylloblattoids and most Isoptera. The t'horacic sclerites of the Grylloblattoids and other Orthopteroids are very like those of the Isoptera, and the evidence from this source would lend support to that of the head capsule in indicating that the Isoptera are very like the Protoblattoid ancestors of the Orthopteroid group of insects.
While the head of such Blattids as Cryptocercus is rather suggestive of the precursor of the Orthopteran type of head, and the head capsule of such primitive Mantids as Eremiuphila exhibit certain features likewise suggestive of the st,arting point
19261 The Affinities of Grylloblatta 81
of the evolution of the Orthopteran type, the head of a typical Blattid or Mantid does not resemble that of a typical Orthop- teron as much as the head of a typical termite does, and the thoracic sclerites of the Blattids and Mantids are not as similar to those of the Orthoptera as the thoracic sclerites of the Isoptera are, so that in general, the Isoptera are nearer to the ancestors of the Orthopteroids than the Blattids and Mantids are, although in the character of their terminal abdominal structures, the Blattids and Mantids approach the Orthopteran type more closely.
In the slenderness of the lacinia and galea, the maxilla of Grylloblatta (Fig. 1) resembles that of Gryllotalpa and the Der- maptera, but the stipes of Grylloblatta is not divided into the Fig. 1
Fig. 2 Fig. 3 Rg. 4
Fig. 1, Ventral (posterior) view of labium, maxilla, and sinistral half of head. Fig. 2 Frontal view of head capsule.
Fig. 3, Ventral (posterior) view of dextral mandible. Fig. 4, Antenna.
peculiar subdivisions present in these two Orthopteroids. The
maxilla of a typical Isopteron or Blattid would readily serve as. the starting point for evolving the types of maxillae occurring in the Grylloblattids and Dermaptera; and the Isoptera seem to be
82 Psyche [June
somewhat nearer than the Blattids are to the Orthopteroids, in the character of their maxillse.
The character of the labium of Grylloblatta (Fig. 1) clearly shows that this insect is Orthopterous or Orthopteroid, since it is only in the Orthoptera that I have found a separate and dis- tinct, well-chitinized mentum of the type shown in Fig. 1, mn. The labium of Grylloblatta lacks the transverse gular plate characteristic of all Dermaptera; and the type of labium ex- hibited by the Orthopterous insects might be derived more readily from Isopteroid or Blattoid precursors. It is rather surprising that the maxillae and labium of the Phasmids which I have examined are not as similar to these structures in Grylloblatta as the maxillae and labium of the Em- biids are. This, however, is doubtless due to the fact that my material is not as suitable as it might be to indicate the real relationships involved, and there are certain features of the submental region of the Phasmid labium, for example, that indicate a much closer relationship to the Orthoptera should be expected in the Phasmids than in the Embiids. The mandible of Grylloblatta (Fig. 3) is very like that of such Orthoptera as Gryllotalpa, and resembles the type occurring in the Embiids quite closely. The mandible of Grylloblatta is not as much like that of the Phasmids and Dermaptera as one would expect, but it resembles the Dermapteran type as much as any. The resemblance to the Isopteran or Blattid type is notvery marked, so that the evidence of the mandibles it not of great phylogenetic value.
The antenna of Grylloblatta (Fig. 4) is remarkably like that of Embia not only in the number of the segments con~posing it, but also in the relative sizes of the individual segments. The antenna of Grylloblatta is also very like that of such Phasmids as Timema and this type of antenna was apparently inherited from a commoil Protorthopteroid source. Among the true Orthop- tera, the type of antenna found in the Acridids (Locustids) and their allies approaches the Grylloblattid type more closely than is the case with the antennae of the Tettigonioids and Grylloids, which is rather surprising in view of the fact that Grylloblatta is more closely related to the Tettigonioid and Grylloid Orthoptera
19261 The Affinities of Grylloblatta 83
than it is to the Acridids and their allies. The Grylloblattid
type of antenna approaches that found in certain primitive Dermaptera and Isoptera more closely than it does the Blattid or Mantid type of antenna, and the antennae of certain Grylloids and Tettigonioids are much more like the antennae of the Blattids and Mantids than is the case with the antenna of Grylloblatta, although in a few Blattids, I have found a suggestion of the Grylloblattid type of antenna.
It is quite possible that there were two tendencies in the Protoblattoid ancestors of the Orthopteroid insects. One ten-
dency was to retain the multiarticulate type of antenna with many annular segments in the basal region of the flagehm while the segments in the distal region of the flagellum tended to become more cylindrical. This tendency, exhibited by most Blattids and Mantids, affected the development of the Grylloid and Tettigonioid types of antennae. The second tendency among the Protoblattoid ancestors of the Orthopteroid insects was toward a reduction in the number of antenna'! segments, and to increase the proportion of cylindrical segments, while only a few segments in the basal region of the flagellum remain short, or approach the annular type to any degree. This ten-
dency affected the Phasmid, Dermapteran, and Grylloblattid descendants of the Protorthopteroids more than any others. In the main, the evidence of the head-capsule and its ap- pendages is in harmony with that from other sources which supports the views as to the interrelationships of the Orthop- teroid and Isopteroid insects proposed by Crampton, 1924; and according to these views the insects in question were grouped as follows :
Section Orthopteradelphia (Orthopteroid insects, sensu lato) Superorder Panisoptera (Isopteroid insects) Orders Protodictyoptera (Protoblattids-f ossil) Dictyoptera (Blattids and Mantids)
Superorder Panorthoptera (Orthopteroid insects, sensu stricto)
Orders Protorthoptera (Fossil)
Orthoptera (Saltatoria and Grylloblattids) Dermaptera
Superorder Panplecoptera (Plecopteroid insects) Orders Protoplatyptera Hadentomoidea-fossil) Platyptera (Embiids)
The Plecopteroid and Orthopteroid insects were descended from Protorthopteroid forebears which arose from the Proto- blattoid ancestors of the Isopteroid insects, so that the ancestral types in the common Frotorthopteran-Protoblattid stem gave rise to the lines of descent of the Isopteroid, Orthoptero d, and Plecopteroid insects which comprise the Orthopteroid nsects in the broad sense of the term The Palaeorthoptera such as Synar- rnoge, serve to connect the common Protorthopteran-Protoblattid stem with the Paleeodictyoptera, wh'ch are very like the ancestral- types giving rise to the winged insects in general. Crampton, G. C.
1915. Thoracic Sclerites and Affinities of Grylloblatta. Ent. News, 26, p. 337.
1917. Antennae 0." Grylloblatta and Embiids. Canadian Ent., 1917, p. 213.
1917. Ovipositor of Grylloblatta and Related Insects. Jour. New York Ent. Soc., 25, p. 225.
Lateral Head and Prothoracic Regions in Grylloblatta and Related Insects. Ent. News, 28, p. 398. 1922. Evolution of Insects Indicated by the Venation. Can- adian Ent., 1922, p. 206.
Maxillae of Grylloblatta and Related Insects. Jour. New York Ent. Soc., 31, p. 77.
Phylogeny and Interrelationships of Insects. Jour. Ent. Zool., 16, p. 33. 1926.
Sclerites of Grylloblatta and
Other Insects. Trans. American Ent. Soc., 61. Imms, A. D.
1925. Textbook of Entomology.
19261 The Affinities of GryIIoblatta
Walker, E. M.
1919. Genitalia of Male Grylloblatta. Canadian Ent., 1919, p. 131.
1922. Terminal Abeominal Structures of Grylloblatta and Re- lated Insects. Ann. Ent. Soc. America , 15, p. 1. ABBREVIATIONS
a.. . Basal process of lacinia
ac . . Anteclypeus
af . . Antennifer
an.. Antennale (basantenna)
ant. Antenna (basal segment)
bc. . Basicardo
bm. .Basimaxillary membrane
cs . . Coronal suture
dc. . Disticardo
e . . . Compound eye
fr.. . Frons
fp. . Frontal pits (frontocavse)
is.. . Frontal suture
ga. . Galea
ge . . Gena
g1. . Glossa
gp. . gular pit
gu.. Gular region of membrane
hc. . Hypocondyle (gnathocon-
in. . Incisors
la. . Lacinia
lp . .Labial palpus
lr . . . Labrum
Is. . . Labiostipes
m.. . Mandibulare (basimandibu-
mp.. Maxillary pal pus
pa. . Parietals
pc . . Postclypeus (epistoma)
pd. . Pedicel
pge . Postgena
ppd. Post pedicel
pr.. . Postgenal ridge
pst. . Parastipes
sc. . . Scape
st ..... Stipes
ts.. . Temporal suture
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