THE NEURO-SECRETORY CELLS OF THE BRAIN, 

 THE CORPORA CARDLiCA AND THE CORPORA ALLATA 

 DURING CASTE DIFFERENTIATION IN AN ANT 



Нсйросекреториые клетки мозга, кардинальных и прилеясащпх тел в течение 

 дифференцпровкн муравьео на касты 



М. V. BRIAN 



(The Nature Conservancy, Furzebrook Research Station, 

 Wareham, Dorset, England) 



The differentiation between worker and queen in the ant Myrmica rubra L. 

 starts in the last larval instar. This instar can be conveniently divided into 

 an early period (called A) when metamorphosis does not occur if the larva 

 is starved and a later one when it does (called B). During the A period all 

 the imaginai buds grow and the brain moves out of the head into the thorax 

 (pushed quite probably by the growing antennal buds). During the В period, 

 the buds continue to grow though they also differentiate, the legs into segments 

 and the ovaries into tubules. Finally, the larva stops feeding, and pre-pupal 

 and pupal periods follow. 



In the A period at liaK transit of the brain, a complicated diapause super- 

 venes in larvae that reach this stage in late summer. Four blending periods are 

 conveniently distinguished: first a period of complete stasis, then one of slow 

 conchange ллdth high growth to development ratio (roughly August and Septem- 

 ber) then a period when if forced artifically, the larvae Avill suddenly meta- 

 morphose into workers (roughly October — November) and finally a cold 

 phase which establishes the abihty to sustain rapid growth and form queens 

 (roughly December and January). Most queens are produced from diapause 

 larvae and most workers from non-diapause ones but the distinction is not 

 sharp. 



During the A period after the brain is half-way, the smaller and less vigorous 

 larvae are determined as workers; this can be recognised by the fact that the 

 wing and ovary buds stop growing, whilst the leg and antennal buds (and 

 doubtless others that are less convenient to observe) actually groAv and diffe- 

 rentiate more quickly than in queens (provided of course that they have food 

 supplied from current intake or from reserves), so that a smaller pupa is 

 formed usually at an earlier time. The small wing buds never inflate and are 

 lost in the body wall of the pupa, but the ovary even though it never splits 

 into tubules, becomes a functional egg-tube. Undetermined larvae continue 

 to grow isometrically with a low development rate and if starved produce 



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