192 MR. Т. Н. CORRY ON ASCLEPIAS CORNUTI. 
regularly dichotomous in their arrangement, and this can only occur by one of the 
projecting corpuscular appendages, either with or without a pollinium attached to it, 
becoming caught in the open lower extremity of an alar chamber; it is then drawn upwards 
in the cavity, its pollinium, if it has one, is usually detached in the lower part, and then 
in any case the appendage simply passes upwards as the insect raises its leg and lifts out 
the corpusculum situated at the apex of the chamber, along with its pair of appended 
pollinia. I am unable to conceive that this dichotomous form can be brought about 
in any other way, since the alar chamber is in all cases of much too contracted dimensions 
to admit of the passage of any form of combination except a unilateral series such as 
that previously mentioned, 7. e. а combination with a single pollinium directly attached to 
each eorpuseulum save the last, which has two pollinia. Several of the most curious and 
complieated of these dichotomous series which have actually been met with will be found 
figured in the plates (figs. 20 & 21). Very frequently in those combinations which are 
found attached to displaced but unremoved corpuscula the presence of a portion of a 
corpuscular appendage in the fissure of the uppermost corpuseulum of the series indi- 
cates clearly that the combination had once been larger and more complex, but has 
become broken. Ве the combination what it may, in no ease does the connexion occur 
by means of one corpusculum being fastened directly to another, but always by means 
of the remains of the ruptured appendage, or appendages, as the case may be, of one 
corpusculum being each firmly caught in the fissure of another. 
Dr. Hermann Müller quotes * the interesting case of a butterfly resembling a Vanessa 
which was observed by Fritz Müller to visit the flowers of 4. curassavica, L., and which 
had on one leg not less than eleven corpuscula belonging to this Asclepiad ; but of the 
twenty-two pollinia which formerly were appended to these only eight were present, the 
others having in each case gone to fertilize other flowers. In three cases combinations 
are exhibited in his accompanying woodeut t. 
The corpusculum itself never remains in the ајаг chamber, and is very difficult to remove 
and detach from the insect's foot, and may be often attached to the foot when the insect 
is eaught. I have frequently seen bees and flies which, in their repeated visits to flowers, 
had numerous corpuscula with their several pollinia attached to almost every leg, and 
sometimes in combination ; yet these insects did not seem to experience much annoyance. 
Hildebrand mentions | the curious fact that frequently the proboscis of bees which visited 
the flowers of Asclepias Cornuti was not devoid of pollinia, since it also in the search for 
honey had been inserted into and drawn up the alar chamber in the same fashion as the 
foot. "This observation is peculiarly interesting, as affording a sort of transition, though 
purely an accidental one, between the action of insects on the flowers of those Asclepiad 
genera, viz. Gomphocarpus, Centrostemma, and Hoya, in all of which, as in all the species 
of Asclepias, transference of the pollinia is accomplished by means of the hooked claws of 
the feet, and on the other, their action on those like Cynanchum, Vincetoxicum, Boucerosia, 
Stapelia, Araujia, Brot., and Pergularia, L., in which the stiff bristles on the proboscis 
are the agents in carrying off the pollinia. 
* Loc. cit. p. 397, fig. 123. t Compare also Mr. Weale's paper (Joc, cit. p. 53). 
t Bot. Zeit. 1860. 
