648 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of wings, traces of these organs would occur, at least in the larval or 

 the pupal stage. For four years his labours were in vain, and it is 

 only quite recently that he succeeded in demonstrating the rudimen- 

 tary hind-wings in the larvae and pupae of Niptus hololeucus Cam., in 

 which both sexes are apterous, i. c. destitute of hind-wings. The fore- 

 wing occurs in the half-grown larva, but the rudiment of the hind- 

 wing only shows itself much later when the animal is already on the 

 point of terminating the larval stage. 



We have in these rudiments of hind-wings an organ which is 

 either advancing or has retrograded. That it is not an advancing 

 organ, but one in course of disappearance, is shown most decidedly by 

 the circumstance that this, like all retrogressive organs, does not, 

 like those in full function, increase with the development of the 

 individual, but, on the contrary, diminishes. We are therefore justified 

 in assuming that Ni2)tus Jwloleiicus once bore well-developed hind- 

 wings, and that these gradually became aborted in consequence of 

 disuse, until they were finally thrown back into the young stages, and 

 some day will disappear even from these stages. In other wingless 

 beetles this period may have already occurred. 



This abortion of an organ brings after it other transformations of 

 the body. Without the hind-wings the beetles cannot fly. It is 

 therefore not necessary for them to be able to spread out the elytra, 

 the latter rather remain permanently lying upon the back. What is 

 the consequence ? The two elytra grow together to form a firm dorsal 

 shield, such as we find in nearly all beetles which are entirely destitute 

 of hind-wings. At the same time the elytra become convex, and bend 

 round at the sides, so that they embrace the abdomen. In conse- 

 quence of the disappearance of the wing-muscles, the thorax becomes 

 altered. The body acquires quite a different form ; new forms are 

 produced which we call species. 



Clasping Organs, accessory to generation, in Lepidoptera.* — 



P. H. Gosse's observations relate primarily to the Paiiilionid Butter- 

 flies, of which he describes the accessory male organs in sixty-nine 

 species, belonging to two genera, from study of dry specimens. He 

 finds the greatest divergence in the form of these parts between species 

 which appear otherwise closely related, but hesitates to apply their 

 characters to the classification of the group. The manipulation 

 employed was as follows : — One of the anal valves is detached by 

 making incisions along its hinge and then prising it off; the valve 

 is examined, and the attached harpe sometimes detached ; the organs 

 still remaining in the abdomen are usually examined in situ, either 

 dry or after introduction of a drop of water to swell the soft 

 parts. 



The parts described are: — 1. Valves (De Haan), characteristic of 

 the males in Painlio, more or less aborted in a few genera. 2. JSarpes 

 (lateral appendages ? De Haan), one placed in the concavity of each 

 valve ; they are chitinous, transparent plates, varying from colourless- 

 ness to a very dark brown hue ; the margins are usually thickened, 



* Trans. Liuu. Soc. (Zuol.), ii. (1883) pp. 265-345 (8 pis.). 



