On the Affinities of the Grylloblattidae.
Psyche 34(1):36-39, 1927.
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36 Psyche [ ~ e bruary
ON THE AFFINITIES OF THE GRYLLOBLATTIDX
BY A. D, IMMS, D. Sc.,
Rothamsted Experimental Station, Harpenden, England. The family Grylloblattidae includes two known genera viz. Grylloblatta Walk. (N. America) and Galloisiuna Caudell (Japan). In its morphological characters it is evidently the most primitive living family of Orthopterous insects. Viewed from the phylo- genetic standpoint, the Grylloblattidse are of exceptional interest in that they combine features of the Orthoptera (sensu lat.) Isoptera, Dermaptera and Embioptera. Most of these characters have already been pointed out by Walker (1914) and in a series of papers by Crampton. The possession of a combination of "synthetic" characters, that are exhibited also in other groups, has rendered it difficult to settle the taxonomic position of the Grylloblattidae and the affinities of the latter have consequently given rise to some divergence of opinion. In so far as the main characters are concerned, Walker considered that they are nearest allied to the family Blattidae of the Orthoptera Cursoria. The present writer (1925) also maintained that the Grylloblattidse are more closely related to the Cursoria than to the Saltatoria. On the other hand, Crampton in his most recent publication (1926) on the subject emphasises his previous opinion that the family should be placed along with the Orthoptera Saltatoria. In en- deavouring to clear up the cause of this bone of contention it is useful to enumerate the principal characters that distingiuish these two main divisions of the old order Orthoptera and they are summarised below.
ORTHOPTERA CUBSORIA. (Blattidse and Mantidae, to- gether with the more distantly related Phasmidse). Legs usually
of approximately equal size and the hind pair not modified for leaping: tarsi 5-jointed. Sound producing organs wanting. Cerci most often multiarticulate, often with 8 to 15 or more joints. Ovipositor reduced and concealed. Penis asymmetrical. ORTHOPTERA SALTA TORIA (Orthoptera sensu strict0 : Acridiidse, Tettigoniidse and Gryllidse). Legs of unequal size, Ps~che M36-19 (1027). hup Yftisycht enlclub org/14/34-0% html
19271 On the Affinities of the Grylloblattidce 37 the hind pair modified for leaping: tarsi never more than 4- jointed. Sound producing organs almost always present. Cerci never multiarticulate. Ovipositor well developed and almost always exserted. Penis bilobed and symmetrical. On the characters enumerated above it may be said that the Grylloblattidse only differ from the Cursoria in the possession of a well developed exserted ovipositor. It is, however, necessary to examine certain other criteria and not base a definite conclusion solely upon this diagnosis. Furthermore, several of the features stressed by Crampton in maintaining his point of view need some comment.
(1) Absence of ocelli. This character is of little phylo- genetic value as ocelli tend to degenerate or disappear in various Orthoptera. Thus, among the Cursoria they are reduced or wanting in some apterous Blattidse as well as being absent in many Phasmidse. Their absence, therefore, is no criterian of affinity with the Saltatoria.
Multiarticulate cerci only occur in the Blattidse and the related family Mantidse. Unjointed setif orm cerci are found in the Gryllidse but there is no indication that this superficial similarity to the same, but multiarticulate, organs in the Gryllo- blattidse is anything more than a parallelism, induced perhaps, by a similar terrestrial life.
Dr. Crampton has already pointed out the structural similarity that exists between the terminal abdominal segments of the Grylloblattidse and Mantidse. He has likewise stressed the similarity of the coxse, trochanters and divided trochantins, as seen in the Grylloblattidse and Blattidae, so no further com- ment here is needed.
(4) The various Isopteran characters ,displayed in the Grylloblattidse, and emphasised by Crampton, afford indirect support to the relationship of that family with the Blattidse. It is generally accepted by such competent authorities as Holm- gren and others that the Isoptera are closest related to the Blattidse on the sum total of their characters. Evidences of affinity of the Grylloblattidse with the Dermaptera and Embiop- tera have very little bearing upon their systematic position within the Orthoptera.
38 Psyche [February
The Saltatorial affinities of the family are undoubted as Walker was the first to demonstrate. My contention is that they are insufficient to warrant its transference from the Cur- soria. The most important character is the exserted ovipositor ot the Tettigonid type but here, as Walker has shown, it is constructed on a somewhat more primitive plan. The presence of the vaginal orifice between sterna 8 and 9 affords another character of the Saltatoria but is it also shared with the Phasmidse. The general resemblance of the head to that of the Gryllidse has been pointed out by Walker and subsequently by Crampton. The antennae, on t'he other hand, show no such affinity and are definitely Embiid in character. The mouth-parts yield no decisive data although in some particulars they exhibit slight, but unconvincing, resemblances to those of the Gryllidae. (6)
The full evidence of internal anatomy is at present unavailable but when Miss Ford's study of this aspect is com- pleted we shall be in possession of data of considerable impor- tance. Her recent study of the abdominal muscles (1924)) however, indicates that the Grylloblattidse betray Blattid and Mantid relationships rather t,han affinities with the Saltatoria. In conclusion, it is hoped that the present article sufficiently explains the grounds for including the Grylloblattidge as a family of the group Cursoria of the Orthoptera (sensu lot.) I wish to thank t'hank Miss Norma Ford for kindly supplying me with a well preserved example of the species Grylloblatta campodeifomis. Crampton, G. C.
The Affinities of Grylloblatta indicated by a study of the Head and its Appendages. Psyche, vol. 32, pp. 78-85, (other papers by this author are listed here). Ford, N.
A Comparative Study of the Abdominal Musculature of Orthopteroid Insects. Trans. Roy. Canad. Inst., vol. 14, pp. 207-319: pis. 7-23.
19 271 On the Affinities of the Grylloblaattidce 39 Imms, A. D.
1925. A General Textbook of Entomology. London. Methuen & Co., Ltd.
Walker, E. M.
A new species of Orthoptera, forming a new Genus and Family. Can. Entom., vol. 46, pp. 93-99. 1919. On the Male and immature state of Grylloblatta campodeiformis Walker. Can. Entom., vol. 51, pp. 131-139.
The Terminal Structures of Orth~pt~eroid In- sects: a Phylogenetic Study. Ann. Ent. Soc. America, vol. 12, pp. 267-316: vol. 15, pp. 1-76.
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