SUPPLEMENT TO PSYCHE. 



(lid not find a single Nitidulid beetle 

 either in the larva or adult. Of insects 

 bflonging to other orders, there is quite 

 abundant in the pulp of the giant cactus 

 a Forficulid {Spongophora brtinnei- 

 peimis Serv. ) and two Pseudoscor- 

 pions ( Chelifer n. sp., and Chelanops 

 sp. 



It is evident that the giant cactus, 

 whenever it is Injured, furnishes a 

 retreat and food for a very large fauna 

 of insects, especially Coleoptera. The 

 trouble is to find one which is attacked 

 at all by insects. 



Tucson, Ar., Dec. 2S, 1S96. 



I have to add to my last letter an 

 interesting discovery which I made this 

 afternoon in continuing my study of the 

 fauna of the giant cactus. It is stated 

 that a small owl makes its nests in 

 holes which are excavated in the trunks 

 of this cactus by a woodpecker and I 

 have frequently noticed that holes are 

 seen in the trunks S or 10 to 15 feet 

 above the ground. To-day I cut down 

 with my hatchet one of these great 

 plants in which was a perforation far 

 above my reach. On examining the 

 fallen trunk I found the hole contained 

 abundant excrement of some bird but 

 no nest. However, there were some 

 curious ticks which remind me of the 

 Ornithodorus of the Gopher tortoise of 

 Florida and which I suspect to be 

 parasites of the bird that made and used 

 the hole. More interesting still it was 

 to find that the hole gave admission to 

 the insect fauna of the cactus, princi- 

 pally to the great Cactophagus larva 



which ploughs its long galleries into 

 the woody skeleton of the plant and 

 which is followed by the immense 

 dipterous (Volucella) maggots and all 

 the multitudinous insects that follow in 

 their train, among their number perhaps 

 the most important being Dactylos- 

 tcrniim cacti and its larvae. The 

 depredations of these insects cause the 

 rotting of the cactus especially within 

 the internal bundle of woody rods 

 which alone enables these gigantic 

 plants to uphold their great weight. 

 Even this woody bundle is preforated 

 and entirely blackened and rotted, while 

 the whole interior of the plant becomes 

 a yet black mass of the consistency of 

 soft mud. The cactus thus attacked 

 sends out branches just below the 

 wound in the exterior, and the first 

 result is that the huge trunk breaks 

 apart at that point and the upper portion 

 falls at length to the ground. It is this 

 process that produces the nunieious 

 examples of these cacti in which the 

 upper half of the stem is missing, 

 while the older portion supports a 

 number of great branches. Without 

 the intervention of the bird in making 

 its burrow the insect fauna of the cactus 

 could never exist; for no insect can 

 penetrate the tough and silicious rind 

 of the plant. It is most remarkable 

 how quickly the plant repairs a casual 

 wound extending into its pulpy exterior. 

 The wounds made Saturday afternoon 

 with my hatchet are to-day (Monday) 

 so hardened on the exterior that no 

 ordinary insect could eft'ect an entrance. 

 The surface already presents an incipient 



