234 



THE AGRICaLTURAL NEWS. 



.Tqly 22, 1911 



INSECT NOTES. 



INSECT 



POLLINATION 

 PLANT. 



OF AN AROID 



111 1894, Professor C. V. Kiley and Mr. H. G. Hubbard 

 visited Montserrat, to investigate the occurrence of scale 

 insects on lime trees in that island. Mr Hubbard, during 

 his visit, which extended over a considerable period of time, 

 made many notes and observations on the local insects and 

 plants One of the.'^e observations appeared as an article in 

 Insect Life (Vol. VII, p. 340, March 1895), under a heading 

 similar to that given above. The following account is 

 abstracted from the article mentioned. 



The plant observed was a species of Philodendron, which 

 is related to the eddoe and the aroids, and is one of the 

 largest of the climbing jungle plants. The tiower case is flask- 

 shaped ( Fig. 1 2, a ife b), and when cut open, ' is found to consist 

 of a thick and leathery 

 s p a t h e, wrapped i n 

 a spiral about an upright, 

 cylindrical spadix. The 

 envelo[iing spathe tightly 

 clasps in its embrace the 

 up|>er, jxillen-prodiicing 

 portion of the spadix, but, 

 expanding below, leaves 

 the fruiting portion free, 

 in a cavity which is 

 partly filled with a muci- 

 laginous liquid. All evap- 

 oration is prevented by 

 the overlapping of the 

 spathe, and the floral 

 organs thus seem to be 

 destined to self-fertiliza- 

 tion, most rigidly enforc- 

 ed. Indeed, it is difficult 

 to conceive how any 

 fertilization could be 

 accomplished by the plant 

 it.self, since the pollen 

 tubes of the spadix, 

 l)eing tightly inrolled by 

 the inner folds of the 

 spathe, are unable to 

 give forth their fertiliz- 

 ing grains.' 



Mr. Hubliard's article 

 was illustrated by means 

 of a plate preiiared from 

 diagrammatic drawings, 

 that illustration 



The maturing flow-ers are infested by numerous larvae 

 of sap-loving beeUes and tlies, which .swaim in the flower 

 cases, feeding upon the envelope and breaking it down, until 

 the ripened fruits at the base of the spadix are entirely 

 exposed, to be carried away by birds and other agencies for 

 the dissemination of the seed. 



The immature inliorescence at fir.st contained no insects, 

 but in every instance a brownish spot, apparently caused by 

 a rot fungus, appeared at the same position on the spathe. 

 This, as is indicated at a, in Fig. 12, is at the extreme edge of 

 the overIapi)iiig portion of the spathe, just opposite a deep 

 sinus in the margin. 



It apjiears from the observation.'? recorded that the fungus 

 »pot, which often grows to the size of a shilling [liece, occurs 



Fig. 12 hi 



Fli:. 12. IViI.LINATlON 



been re-drawn from 



at a point where a sap-feeding insect has gnawed the 

 epidermis of the spathe, in an attempt to penetrate the floral 

 organs within. 



The insect which occurs in this relatioo is a small 

 beetle, which has been identified a.s Jficrostola luten, Murray 

 (see Fig. 12, c). Mr. Hubbard invariably found a pair of these 

 insects between the folds of the spathe. The process of 

 gaining an entrance to the inside of the spathe is a rather 

 long one, but the choosing of the spot where the sinus in the 

 edge reduces the distance to be traversed, and the action of 

 the rot fungus in softening the tissues, makes it shorter than 

 it would be otherwise. 



The Macrostola beetles enter the cavity of the flower case, 

 near the level of the surface of the contained liquid, and, 

 strangely enough, they accomplish their entrance without 

 leaving an opening for other insects to follow them. This 

 is due to the fact that, in its early stage of growth, the 

 fungus causes a shrinkage, which closes the slight aperture 



through which the beetles 

 have entered. 



Immediately on enter- 

 ing the flower case, this 

 pair of beetles makes its 

 way to the pollen-bearing 

 portion of the spadix, 

 forcing a passage between 

 the inner surface of the 

 spathe and the anthers. 

 The feirale deposits eggs 

 as she proceeds, and 

 a numerous colony of lar- 

 vae is soon produced. 

 The larvae live and com- 

 plete their growth w-ithin 

 the flower case, feeding 

 on the pollen, and by 

 their feeding, and burrow- 

 ing in the polleniferons 

 portion, cause the spadix 

 to liberate quantities of 

 a mucilaginous liquid, 

 which carries down masses 

 of pollen to the cavity 

 at the base of the spadix. 

 Every portion of the inter- 

 ior of the cavity is covered 

 with this sticky mixture of 

 mucus and pollen. 



The beetle larvae pass 

 into the pupal stage, which 

 is followed by the emerg- 

 ence of the adults of a new brood. The parents of this 

 brood — the original invaders of the flower case — have pene- 

 trated to the tip of the .spadix, where their dead bodies may 

 be found. 



About this time, the continued devehipnient of the spot 

 of rot fungus has caused an opening in the spathe, permitting 

 the entrance of a great number of insects, which feed on sap 

 and dead tissue. As a result, the spathe breaks down and 

 falls away, and the liquid escapes. 



The beetles are then, by the demolition of their domicile, 

 forced to betake themselves to neighbouring flowers of the 

 same kind, where they mate and the processes just described 

 are repeated. They bear with them, in the pollen paste 

 Avith which their bodies are plentifully bedaubed, the material 

 necessary for the fructification of the new inflorescence into 

 which they enter. 



Ol- l'llIL<i]lENlll;oN. 



