140 HYMENOPTERA 



become known, and as yet has been but little inquired into. The 

 difference between the thoracic structure in the case of the winged 

 and wingless females of certain species (Fig. 55, and in vol. v. 

 fig. 339) is enormous, but in other species this difference appears 

 to be much less. The ordinary distinctions between the queen- 

 female and worker-females appear to be of two kinds; firstly, 

 that the former is winged, the latter wingless; 1 and secondly, that 

 the former possesses a receptaculum seminis, the latter does not. 

 In a few cases it would seem that the dimorphism of winged 

 and wingless forms is not complete, but that variability exists. 

 Intermediate conditions between the winged and wingless forms 

 are necessarily rare ; nevertheless a certain number have already 

 been detected, and specimens of Lasius alienus have been found 

 with short wings. In rather numerous species some or all of 

 the fertile females depart from the usual state and have no wings ; 

 (a similar condition is seen, it will be recollected, in Mutillides 

 and Thynnides of the neighbouring family Scoliidae). A di- 

 morphism as regards wings also exists in the male sex, though it is 

 only extremely rarely in ants that the males are wingless. Never- 

 less a few species exist of which only wingless males have been 

 found, and a few others in which both winged and wingless 

 individuals of this sex are known to occur. The wingless males of 

 course approach the ordinary workers ( = infertile wingless females) 

 in appearance, but there is not at present any reason for 

 supposing that they show any diminution in their male sexual 

 characters. The distinction between workers and females as 

 based on the existence or non-existence of a receptcwulum seminis 

 has only recently become known, and its importance cannot yet 

 be estimated. The adult, sexually capable, though wingless forms, 

 are called ergatoid, because they are similar to workers ('E^ar???, 

 a worker). 2 



1 The student must recollect that the winged female ants cast their wings 

 previously to assuming the social life. The winglessness of these females is a 

 totally different phenomenon from that we here allude to. 



2 See Forel, Verh. Ges. deutsch. Nalurf. Ixvi. 1894, 2, pp. 142-147 ; and Emery 

 Biol. Centralbl. xiv. 1894, p. 53. The term ergatoid applies to both sexes ; a species 

 with worker-like female is ergatogynous ; with a worker-like male ergatandrous. 



