T. J. Walker.
Deciduous Wings in Crickets: A New Basis for Wing Dimorphism.
Psyche 79:311-314, 1972.

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DECIDUOUS WINGS IN CRICKETS:
A NEW BASIS FOR WING DIMORPHISM
BY T. J. WALKER^
Department of Entomology and Nematology
University of Florida, Gainesville 32601 Dimorphism in wing length occurs in species of at least seven in- sect orders (Richards, 1961). It is conspicuous in many species of crickets. Crickets with the folded metathoracic wings extending be- yond the tegmina are termed macropterous, and those with the folded metathoracic wings covered by the tegmina are termed micropterous (Alexander, 1961, 1968). Since flying crickets - such as those fly- ing to light traps- are always macropterous, it seems safe to con- elude that micropterous crickets cannot fly. It seems probable, though the evidence is sparse, that macropterous individuals generally do fly and that wing dimorphism in crickets has the same behavioral cor- relation with emigration that it has in aphids (Kennedy and Stroyan, 1959).
In studying three species of short-tailed cricket (A~ogryZZus)~, I noted dimorphism in wing length. Most specimens had no' visible metathoracic wings (i.e. were micropterous), but 5% of those of the U. S. species and about 20% each of two West Indian species had conspicuously protruding metathoracic wings (i.e. were macrop- terous). At least 5 of the 16 macropterous West Indian specimens were collected at light, but none of the 4 macropterous specimens of the U. S. species were. Three of these 4 were recently molted specimens from a laboratory colony and the other was a teneral specimen dug from its burrow in the field. Obviously none had ever flown. In studies of the same species Weaver and Sommers (1969, p. 338) also noted macroptreous teneral specimens, and in addition described behavior that accounts for the absence of macropterous in- dividuals among non-teneral specimens: "When the cricket first transforms into the adult stage, the wrinkled, whitish hindwings extend for some distance beyond the posterior edge of the forewings . . . . . . Usually within 24 hr the hindwings are broken off at the base and eaten."
'This study was supported by NSF Grant GB-20749. Florida Agricul- tural Experiment Station Journal Series No. 4576. 'The three species are presently known as A. muticus (De Geer), but they will be given distinctive binomials in a paper now in press (Walker 1973).
Manuscript received by the editor October 9,1972



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.?I2 Psyche [December
Prompted by these clues, I examined more than 20 "micropterous" specimens of each of the three species of Anurogryllus. All had wing stumps rather than short wings. I pulled with tweezers on one of the wings of an alcohol-preserved, non-teneral macropterous speci- men. The wing tore loose with difficulty but left a stump like those of the "micropterous" specimens. Apparently all the specimens had once been macropterous, and the dimorphism in wing length in each of the three species is based on a dichotomy in wing deciduous- ness rather than a dichotomy in wing length in the newly formed adult.
DISCUSSION
The term micropterous is inappropriate for crickets with the stumps of deciduous wings. The term dealated has been used for similar cases in other insects and seems appropriate here. So far as now known, dealated AnurogryZZus are originally ma- cropterous rather than micropterous, but since wing shedding has not been observed in either of the West Indian species, the length of the shed wings is unknown. Furthermore the timing of shedding is not known for the West Indian species.
One possibility is that it
occurs only in teneral adults, as in the U. S. species. If this be the case, shedding the wings could depend on either the wings being weakly attached to the stumps or on wing-removing behavior or on both. If some or all teneral adults are competent both to retain and to shed their wings, their remaining macropterous or becoming de- alates would most likely be an adaptive response to some aspect of their environment. For example a stimulus associated with dense population might inhibit wing shedding and promote emigration. A second and contrasting possibility concerning the timing of wing shedding in West Indian Anurogryllus is that none sheds its wings while teneral and all or nearly all individuals disperse by flight before losing their wings. Situations analogous to this possi- bility occur in termites, ants, and perhaps certain zorapterans (Imms, 1957). I know of no case analogous to the first possibility (i.e.
dimorphism with nonmigratory individuals shedding potentially func- tional wings). Certain Australian roaches of the genus Panejthia are apparently like the U. S. Anurogryllus - i.e. all individuals
shed well-developed wings shortly after the final molt ( Mackerras, 1970; P. 273).
The extent to which crickets other than Anurogryllus have decid- uous wings is unknown. If such wings were characteristic of any of the species in which wing dimorphism has been carefully studied,



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they would have been reported. The only instances known to me of wing shedding in crickets other than AnurogryZZus are in Gryl- lus. R. D. Alexander (personal communication ca. 1960, 1972) told me he had seen a Gryllus bimaculatus De Geer female pull off and eat the wings of a courting male. In handling living macrop- terous G. rubens Scudder, I have noted that the wings occasionally detach with only a slight pull. More recently I have tried pulling the wings from alcohol-preserved specimens of G. rubens. In both macropterous and micropterous individuals the wings were often easily detached. They tore just distal to the axillary sclerites and left stumps like those in Anur~~ryllus. These specimens had been freshly killed within the first week of adult life and had never flown. Of more than 100 such specimens examined none was al- ready dealated.
Two attributes of wing shedding that have probably contributed to its evolution are ( I ) it sometimes aids escape from predators (cf. G. rubens escaping from my grasp) and (2) it allows functionless or no-longer-functional wings to be eaten (cf. many insects, includ- ing crickets, eating their exuviae, apparently to nutritional advan- tage).
SUMMARY
In three species of Anurogrylluf that are superficially dimorphic in wing length all "micropterous" individuals have the stumps of longer wings. The dimorphism is in the occurrence of wing shed- ding and is not known to correlate with a dimorphism in wing length.
REFERENCES
ALEXANDER, R. D.
1961. Aggressiveness, territoriality, and sexual behavior in field crickets (Orthoptera : Gryllidae) . Behaviour 17 : 130-223. 1968. Life cycle origins, speciatioal, and related phenomena in crickets. Quart. Rev. Biol. 43 : 1-41.
IMMS, A. D.
1957. A general textbook of entomology, 9th ed. (rev. by 0. W. Rich- ards and R. G. Davies). Methuen, London. 886 p. KENNEDY, J. S., AND H. L. G. STROYAN
1959. Biology of aphids. Annu. Rev. Entomol. 4: 139-160. MACKERRAS, M. J.
1970. Blattodea (Cockroaches), p. 262-274, In Div. Entomol. Com- monwealth Sci. Ind. Res. Org., Camberra, Insects of Australia. Melbourne Univ. Press, Melbourne.




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RICHARDS, 0. W.
1961. An introduction to the study of polymorphism in insects, p. 1-10, In J. S. Kennedy (ed.), Insect polymorphism. Symp. No. 1, Royal Entomol. Soc. London.
WALKER, T. J.
1973. Systematics and acoustic behavior of U. S. and Caribbean short- tailed crickets (Orthoptera : Gryllidae : Anurogryllus) . Ann. En- tomol. Soc. Amer. 66 : (in press).
WEAVER, J. E., AND R. A. SOMMERS
1969.
Life History and habits of the short-tailed cricket, Anurogryllus muticus, in central Louisiana. Ann. Entomol. Soc. Amer. 62: 337-342.




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