140 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Pore plates, pe'_ r s, Forel's flasks, pit pegs, and end roils have all been 

 considered as olfactory organs by various authors. Pore plates cannot 



be the olfactory structures in all insects, for they arc entirely absent in 

 Lepidoptera. The pegs cannot be the olfactory structures in all insect-. 

 for they are absent in many male bees and almost wanting in Lepidoptera, 

 although possibly the end rods in butterflies and moths are homologous. 

 According to Vom Rath, pegs are found not only on the antenna? and 

 mouth parts but also all over the body. Nagel also found them else- 

 where than on the antennae. If the pegs are the olfactory structures, 

 and if insects from which the antennae have been cut off are normal, the 

 author asks why such insects do not respond positively, to a slight extent 

 at least, to odours, instead of negatively as most observers claim. 



Spiders can smell, yet they have no antenna?, and the author's 

 negative conclusion is that the antennae in Hymenoptera play no part in 

 receiving odour stimuli. His positive conclusion is that the olfactory 

 pores are the sensory structures. These olfactory pores were observed 

 by Hicks in 1857, and called by him vesicles. He saw them on the 

 bases of the wings, on the halteres, and on the legs of Diptera, on the 

 bases of all four wings in other orders, on the trochanter and femur of 

 all insects, and occasionally on the tibia. He observed the nerves going 

 to them, and suggested that they were olfactory. They have also been 

 studied by Janet. 



Mclndoo describes the various groups of pores in bees, on the bases 

 of the wings, on the legs, on the sting, on the mouth-parts. For the 

 legs of ants the number varies from 463 to 1090. The grand total for 

 a drone bee is 2608, and that is the highest number observed. The 

 olfactory pores consist of inverted flasks in the chitin and of spindle-like 

 sense- jells lying beneath the mouths of the flasks. About two-thirds of 

 the space at the bottom of the flask is occupied by a hollow chitinous 

 cone, continuous with the cuticle. A sense fibre from the outer end of 

 each sense-cell pierces the foot of the cone and enters the pore aperture, 

 where its cytoplasm comes into direct contact with the air and the 

 odorous particles. A fibre from the base of the sense-cell goes to a nerve. 

 The author has no belief in odours getting through a continuous chitinous 

 cuticle. In spiders Hicks's vesicles are represented by the slit-like lyri- 

 forni organs first described by Bertkau. Mclndoo finds them at the 

 distal end of each joint of the legs, pedipalps, chelicerae ; occasionally on 

 the spinnerets and on the ventral surface of the body. 



o. Insecta. 



Myrmecophilous Organs of Larval Lycaena orion.* — R. Ehrhardt 

 describes these interesting structures, which are of two kinds. On the 

 dorsal surface of the caterpillar, in the middle of the 10th segment, 

 there is a longitudinal slit. When this is titillated by the antennae of 

 an ant, it opens, two cushion-like lips are seen, and between them there 

 appears a small drop of secretion which is greedily licked up by the 

 ant. Besides this, there is on the 11th segment a scent-organ which 



* Ber. Nat. Ges. Freiburg, xx. (1914) pp. xc-xeviii (9 figs.). 



