320 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Wing of Lepidoptera and its “Imaginal Disc.”* — Sig.E. Verson 
refers to the general belief that the larvae of Lepidoptera have no 
stigmata on the meso- and metathorax. Such an organ is, however, 
present, and is formed by a circlet of high hypodermal cells radially 
arranged around a common centre. The branch sent from the longi- 
tudinal tracheal trunk to the dorsal side of the stigmata of the second 
and third thoracic rings is long but delicate ; its peritoneum is widened 
out into several berry-like saccules filled with cell-elements. In profile 
these rudimentary stigraates appear as a series of high hypodermal cells, 
which form the basis of a short blind tube. After the second ecdysis 
a special change occurs in these rudimentary organs. The tracheal 
branch connected with them sends off at various points thick tufts of 
capillary air-vessels, which press against the base of the caBcum. 
Gradually increasing in length they form a fold which continues to 
increase in length. The numerous tufts of tracheal capillaries extend 
beyond the inner surface of the two layers of which the developing 
wing consist ; the berry-like saccules are drawn into the wing and con- 
verted into more or less thick tubes, which will form the “ veins.” It 
is clear, therefore, that the wings of Lepidoptera must be regarded as, 
in the fullest sense, organs of respiration. 
System of Integumentary Glands of Bombycidae.j — Signor E. 
Verson gives an account of the glands he has, after much trouble, been 
able to make out in the larva of Bomhyx mori. There are two upper 
and two lower prothoracic glands, and similarly disposed meso- and 
metathoracic glands. The first to the eighth (inclusive) abdominal 
rings have two such glands, and in the eighth ring there is also a second 
pair. These glands, which can be made out in the embryo, persist 
during the whole of the larval period, constantly increasing in size ; 
they are unicellular and function periodically. The author gives a 
short account of the ehanges which these glands undergo, and promises 
details and figures. 
Colour and Veins of Butterfly Wings.| — Dr. J. F. van Bemmelen 
has studied the development of the wings in Pyrameis cardui, Vanessa 
urticee, and Pieris hrassicse, in order to discover how far the ontogeny of 
the colouring and venation sheds light on the phylogeny. The colours 
do not appear suddenly, but on the minute rudiments of wings. The 
colouring of the unravelled pupal wings is, however, very different from 
that in the imaginal state, though with some characters in common. 
The imaginal pattern is compounded from traces of more primitive 
types, both as regards pigmentation and veins. 
Rectal Glands in Coleoptera.§ — Prof. H. T. Fernald has found in 
the alimentary canal of Passalus cornutus a structure which he considers 
homologous with the rectal glands of other groups of insects. He 
describes the details of these organs, and gives reasons for regarding 
them as having a valvular function. This view is based on the facts 
that, (1) They are the best developed and most alike in Insects which 
feed on solid and quite innutritions food ; in those forms with more 
* Zool. Aiizeig., xiii. (1890) pp. 116-7. f T. c., pp. 118-20. 
X Tijdschr. Nederl. Dierk. Ver., ii. (1889) pp. 235-47. 
§ Amer. Natural., xxiv. (1890) j)p. 100-1. 
