PART IIL. | THE MECHANISMS OF FLOWERS. 563 
Delpino has observed Arum italicum to be fertilised by six 
different flies, of the genera Ceratopogon, Chironomus, Sciara, 
LPsychoda, Limosina, and Drosophila (178,-p. 243). In Arum 
maculatum I have only found Psychoda, but it occurs almost 
constantly, and sometimes by hundreds in a single spathe. I 
could often see, on looking down through the grating, that many 
of the prisoners were trying to fly upwards to the light, and 
falling backwards, or trying to crawl out and being repulsed by 
the sharp points. Whenever I broke open a spathe in the third 
Fig. 185.—Arum maculaium, L. 
1.—The whole inflorescence, x 4. 
2.—Transverse section at the level of ab (1), seen from above, on a somewhat larger scale. 
ab, point at which the cage c is closed by stiff hairs, radiating from the spadix; c, cage inclosing 
the spadix with its reproductive organs; d, attractive portion of spathe; e, barren portion of 
spadix, serving as a guide-post; f, cross-section of spathe; g, ditto of spadix; h, stamens trans- 
formed into stiff filaments, 
stage of flowering, I always found a multitude of inmates groping 
about in the thick layer of pollen on the floor of the chamber. 
The Psychodz which I collected were so various in size and colour 
that I supposed I had obtained at least three species; but Herr 
Winnertz of Crefeld tells me that they all belong to the very 
variable species Psychoda phalenoides, L., which is probably the 
same species found by Delpino in Arwim ttalicwm, and identified 
by Rondani as Psychoda nervosa, Schr." 
1 According to Schiner, Psychoda phalenoides, 1.., is identical with P. nervoca, 
Mgn,, and perhaps also with Tipula nervosa, Schrank. 
00 2 
