140 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



is correlated with the metabolic condition. The experiments indicate, 

 but do not prove, that certain changes in metabolism cause the reversals 

 in reaction to light. All nymphs that reversed their light reactions 

 were either stimulated or depressed, but stimulation or depression does 

 not necessarily involve phototactic reversal. J. A. T. 



Life-history of Red-currant Aphis. — Maud D. Haviland {Proc. 

 R. Soc. Edinburgh, 1919, 39, 78-112,9 figs.). This Aphis, J/v/ms 

 ribis, is dimorphic in respect of certain features of the antenna and of 

 abdominal and wing dimensions. The nature of the food, whether 

 healthy or blistered by the attack of the fundatrix, seems to be the 

 determining factor of this dimorphism. The form from healthy leaves 

 is probably identical with M. tchitei Theobald and J/, dupar Patch. 

 The insect is migratory; and in summer colonizes certain Labiatae and 

 other weeds ; but this migration is not obligatory, and the entire life- 

 cycle may be passed on currant. On its summer host this species has 

 been described as Fhorodon galeopsidis Kaltenbach. There is a decline 

 in fertility in the later part of the summer among the forms remaining 

 on currant. This is caused by a lower birth-rate, and not by the shorten- 

 ing of the life of the parent. This decline, together with the attacks of 

 predaceous and parasitic enemies, accounts for the frequent disappearance 

 of the species from the currant in August and September. Both sexual 

 forms may be produced, and eggs may be laid on either host-plant. 

 Males transferred from Labiate to currant can fertilize females on the 

 latter. . J. A. T. 



Wings and Tracheas of Termites.— Claude Fuller {Annals Natal 

 Museum, 1919, 4, 19-102, 9 pis.). The ribs supporting the termite 

 wing are derived from thickenings of the cellular tissue of the de- 

 veloping organ. One of these thickenings is in the form of an 

 ambient, and develops independently around the margin, whilst the rest 

 form about tracheae. Subsequently, that portion of the ambient thicken- 

 • ing which extends along the outer margin is converted into the rib costa. 

 The trachege of the wing-sac develop from two or from three buds, 

 forming very early in nymphal life upon each of the four sections ot the 

 spiracular trunk tracheae within the meso- and metathorax, and not upon 

 the dorsal and ventral longitudinal trunks, as described in other cases. 

 The position and branching of the longitudinal ribs of the wing are 

 almost wholly dependent upon the position and development of the 

 Jongitudinal tracheae, except in the case of the costa, which is not 

 preceded by a trachea. The specialization of the wing-ribs by reduction 

 follows the reduction of the tracheae. A newly-hatched termite shows a 

 framework of comparatively few simple trachea?, from which a multitude 

 of dichotomizing, arborescent, and other trachea? gradually develop and 

 grow. The specialization of the respiratory system is by reduction. The 

 valvular spiracles of the abdomen of the adult are derived by gradual 

 transformation from the occluding apparatus of the spiracles with a fixed 

 opening exhibited by the nymphs. The slit-like spiracles of the 

 abdomen of highly-distended queens in Termes and Odontotermes re- 

 present disruptions of the final valvular spiracles. J. A. T. 



