"GYNANDROMORPHISM" AND KINDRED PROBLEMS. WITH DESCRIPTIONS AND FIGURES OF SOME HITHERTO UNDESCRIBED EXAMPLES. Br E. A. COCKAYNE, M.D., M.R.C.P., F.E.S. CONTENTS. PAGE OCCURRENCE OF GYNANDBOrdORPHIS~L Strnetnre and Cblssification 75 Gynandromorphism associated with Heterochroism . 82 Larvae which showed Heterochroism and produced Gynandromorphons imagines 86 Insects showing segregation of somatic characters (Heterochroism) but no segregation of sexnal characters {Gynandromorphism) 87 Gynandromorphs partly of male type colonr, and partly of aberrational colonr limited to the female sex 93 HEEEDITb, RY AND FAMILIAL NATURE OF G'CNANDRONORPH1S5I 95 Hereditary Gynandromorphism probably of Indirect Descent 97 Hereditary Gynandromorphism probably of Direct Descent. 107 HYBRID G'iCNANDR0~I0 RPHS , 114 GYNAN DRO~IORPHOUS hlONGRELS 116 THEORETICAL EXPLANATIOI~S OF ~YNANDRO~IORPHIShI . i17 ~ONCLUSIONS 127 DESCRIPTION OF PLATES 128 BIBLIOGRAPHY 130 OCCURRENCE OF GY~NDRO~ORPmSM. Structure and Glassificatio~. SEXUAL dimorplfism is so well marked in insects, especially in the Lepidoptel'a, that the two sexes of the same species have sometimes been assigned to different species and even to different genera. Very striking therefore is the appearance of those individuals which show on one side all the characters, size, shape, and cotour of the one sex, and oll the other, those of the opposite sex. Their existence was known 76 " Gynandromorphism" and Kindred Problems long before any dissections were carried out and the term gynandro- morphous or gynandrous was applied to them. The first dissectioo was carried out in 1825 by Rudolphi on a halved gynanch'omorphous Gastropa~ha quercifolia. Later it was recognised that, besides the halved, other forms of gynandromorphism also occur and in this country Westwood drew special attention to these and figured several in his Thesaurus Entomo- lotions Oxo~iensis. The term means no more than the occurrence in one sex of characters belonging to the other, and covers more than one very distinct phenomenon. It is much better known and probably much commoner in insects than in other animals. But of other Arthropods, Bertkau gives examples in various crustaceans and two, in Arachnida, both in spiders. His list includes instances in all the better known orders of the Insecta, in Lepidoptera, Hymenoptera, Coleoptera, Diptera, and Orthop- tera. There is little doubt that it~ is much more frequent in some of these orders s in others, but so much less attention is paid to some and the phenomenon itself is so much less conspicuous in some than in others, that no very exact deduction as tO the relative fl'equency can be drawn. Several thousands have been recorded in Lepidoptera, but in ttymenoptera, which are also carefully worked, Dalle Torre and Friese could only collect 90 examples, though they left out those produced in the Eugster hive of bees, which alone numbered some hundreds. In Lepidoptera it is unquestionably much commoner in some species than in others, as the lists published byHagen, Wiskott, and Schul~z prove. The difference in numbers is real and not apparent, because in Amorpha populi, which heads the Iist, gynandromorphism is not so con- spicuous as in many equally common species, of which 0nly one or two gynandromorphous individuals are known. Schultz in his first two lists of gynandromorphs in Palaeartic Lepidoptera gives A. populi 54~ examples, Saturnia carpini 48, Dryas paphia 39, Lymantria dispar 32, and Polyommatus icarus 22. Five examples are known in bia'ds. Four of these were perfectly halved, a bullfinch, Pyrrhula pyrrhula europaea, Viei[I, described and figured by l:Ieinroth and Poll, a chafl3nch, Fringilla coelebs, Linn., described by Weber, a flicker, Colaptes auratus, Linn., and a species of Dacnis, a South American sugar bird. The fifth, a pheasant described and figured by Bond, was peri~ctly halved, except in the tail, and there was some decussation of sex characters, each feather of both sides being male on the outer and i~male on the inner side. E. A. COCKAY~E 77 In man Gan'igues stated, in 1896, that he knew an individual, who on the lefg side looked like '~z male, on tl~e right like a female. Pargial segregation of secondary sexual characters to opposite halves of the body, has also been recorded by Munde, Oberndorf, and Le Dentre. Lists of gynandromorphous Arthropods have been published by Hagen, Ochsenheimer, Bertkau, Wiskott, and Sehultz. Ochsenheimer divided them into perfecg and imperfect, and L~cor- daire further subdivided them into-- (1) Semilatdral (halved). (2) Superpos4 (intermediate mixed forms). C,.ois (c,'ossed). In addition he pointed out that, in all three tbrms the sexual elements may be in equilibrium, but in the last two one or other sex may predominate to any extent. A very elaborate classification has been made by Dalle Torre and Friese. Group I. Lateral Gy~Tandromo~Thism. 1. Left o~, right ~. (a) Head alone. 2. Right o~, left ~. (b) Thorax alone. 3. Decussating now o~ right. (c) Abdomen alone. now o~ left. (d) Head and thorax. (e) Head and abdomen. (f) Thorax and abdomen. (g) Whole body. Group II. Transverse Gynandromorphism. (Dorso-ventral arrangement.) t. Dorsally o~, ventrally ~. Subdivisions (a) to (g) as 2. Dorsally ~, ventrally o~i in Group I. Group III. Fro~tal Gynandromorphism. (Antero-posterior arrangement.) 1. Anteriorly o~. (a) Head alone. 2. Anteriorly ~. (b) Head and thorax. (c) Thorax of one, head and ab- domen of the other sex. 78 " Gynand~'omorphism" and I('i~dJ'ed Problems Grmq> IV. Mixed Gy~andromo~hisl~. (Lateral, traz~sversal and frontal intermixed.) 1. Left o~. 5. Dorsally o~. 2. Left ~. 6. Dorsally ~. 3. Anteriorly o~, 7. Decussating. 4,. Anteriorly ~. Nearly all gynandrolfforphs fall into the iburth group. The dorso-ventral arrangement of the external characters has been met with once, and the antero-posterior rather more fl'eqnently. I have seen two specimens of Sat~'nia ca~7)ini with a male head and antennae, the rest of the insect being female, and Mr ]3righb has a similar example of O~'gyice antiqua; Sehultz records a Demas coryli with female head and antennae and a male thorax and abdomen. Lateral gynandro- morphism of the external characters, excluding the genitalia, is common. But in a very large number of instances the halving is not quite perfect. From those insects which show an almost complete halving of external characters we pass gradually to those which show a very coarse mosaic arrangement, the male element preponderating on one side and the female on the other, and thence to those where the two elements are almost evenly baItmeed. In others the coarse mosaic is met with, but one or othel' sex greatly preponderates. In others again the mosaic is fonnd finer. A fine nmsaic arrangement, where tl~ere is a very intimate bilateral mixture, gives the "gynandromorphe snperposd," snch as the Pol~om- matus ica~'us figured later (P1. XXIV, fig. 19). The upper side of this is predominantly male, bnt amongst the small patches with blue scales and anch'oconia, less numerous patches of brown scales of female shape occur. Orange scales representing female hmules also occur on the margins. The underside is predominantly female. Wheeler has described "blended gynandromorphs" with the form of one sex, the colours, sculpture or pilosity of the other. In these I believe the mosaic arrangement still holds good, bnt that cells of male and female type are arranged mtmh as the cells in a plant chimaera (graft hybrid). In these the core, which gives the form, is made purely of cells of the one species and the external layer or layers of ceils made pnrely of those of the other species. Cells of intermediate character do not occur in these plants, nor do they, I think, occur in such gynandromorphs, E. A.. COCKAYm~ 79 though there may be a rather intimate mixture of cells of male or female character. The more gynandromorphs one sees the more unsatisfactory does any attempt at classification by external characters appear to be. Unfortunately classification based on internal structure is greatly hampered by the small number of dissections carried odt and described. This is partly due to the difficulty' of dissection, bu~ far more to the value of these specimens, and the reluctance of their owners to allow any examination. The following classification is based on the somewhat less elaborate one suggested in the Entomologisfs Record. I. GENETIC HERMAPHRODITES. Primary sex glands oj" both sexes present. I. Lateral. (a) Ovary on one side. Testis on the other. (b) Two ovaries on one side. Testis on the other. (e) One ovary on one side. Two testes on the other. (d) Two ovaries on one side. Two testes on the other. II. Unilateral. Ovary or testis on one side. Ovary and testis on the other. IIL Bilateral. Ovary and testis on both sides. II. PI~I~ARY SOMATIC HERM~'~ODITES. Sex gland or glands of o~e sex only, but parts of the secondary sexual apparatus, inter'hal or external, of both sexes present. (a) Male type, with one testis or two testes. (b) Female type, with one ovary or two ovaries. In some c~es the glands are perfectly developed, but a partial or completely rudimentary condition is not uncommon, especially in the ovary. 80 " Gynan&'omorphism," and Kindred Problems III. SECONDARY SOMATIC ~-[EICMAPHRODITES. Sex gland or glands of one sex only, secondary sexual apparatus of one sex only, that correspondi~2g to the sex gla~d present. Secondary sexual characters of both sexes present in antennae, wings, or other parts of bcdy. (a) Male type, with one or two testes. (b) Female type, with one or two ovaries. The majority of gynandromorphous insects fall into Group II, primary sbmatic hermaphrodites, relatively few into Groups I and III.