342 



As tbe result of the exauiiiiation of numerous flower-cases, tlie fungus- 

 si)ot was found to increase in area until it reached the size of a shilling 

 piece. Its growth then ceased. In the meantime the tissues aflected 

 by the fungus shrink and finally s])lit. leaving an opening into the 

 cavity of the spathe through which saprophagous insects can enter 

 at will. 



In examining flowers not yet attacked by the fungus, or in which its 

 presence is barely indicated by a slight discoloration, the author of the 

 contrivance is frequently disclosed. This is no other than a sap-beetle 

 of the family Mtidulidic, a pair' of which, male and female, are invari- 

 ably found together, f(ux'ing their thin bodies under the overlai»piug 

 fold of the spathe. Mr. E. A. Schwarz has identified this beetle with 

 Macrostola lutea Murray, described from Cuinana, Venezuela. 



Fig. 33, c gives an outline of the beetle, with its antenna and front 

 leg more enlarg^ed. Tlie hair line at the side of the figure shows the 

 natural size. 



The Macrostolas evidently consume some days in gaining an entrance 

 into the flower-case. In this laborious eftbrt they are materially 

 assisted, first by the plant, which has accommodatingly reduced the 

 distance to be traversed by the beetle by means of the sinus in the edge 

 of the spathe, without, however, in the least degree breaking the seal 

 of the flower-case. The instinct of the beetle in selecting this weakest 

 point for its attack appears to be unerring. Secondly, I believe that 

 the aid aflbrded by the rot fungus, which promptly attacks the surface 

 gnawed by the beetles in their ettbrt to cut a passage onward, is most 

 material in causing the tissues of the thick and leathery spathe to 

 soften and perhaps to warp slightly in shrinking Thus the beetles are 

 enabled to accomplish that which without this assistance would be 

 impossible to their feeble powers. At any rate, the passage of the pair 

 of insects is made without, for the time being, breaking the closely 

 guarded seal of the plant, and they enter into undisturbed possession 

 of their new home. The point of entrance lies just above the surface 

 of the liquid in the cavity. Once inside, the beetles make their way to 

 the s])adix, and force a pa"ssage upward along its polleniferous portion. 

 The female, as she i)roceeds, dex>osits eggs, which soon produce a 

 luimerous colony of larvji^. By the time their i)rogeny are half grown, 

 the j)arent beetles, having fulfilled the measure of their existence, 

 I)erish. Their dead bodies will invariably be found together at the upper 

 end of the spadix, firmly wedged beneath the fold of the spathe, and 

 incased in a thick paste of pollen grains agglutinated by the mucilage 

 of the plant. * 



The brood of larv;e live and complete their growth within the flower- 

 case, feeding upon the pollen, in search of which they burrow and mine 



* A similar life-long attachment and association of a single pair of adult beetles 

 has been noticed by me in the case of Epura'a monogama Crotch, another member of 

 the family Nitidulid;i>. Compare, "Inhabitants of a Fungus." (Can. Ent., vol. 

 XXIV, 1892, pp. 250 ff.) 



