SUPPLE AfENl 10 PSYCHE. 



[May 1899. 



crust which ultimately becomes a woody 

 layer one-fourth an inch thick and so 

 hard that it resists the blow of a sharp 

 hatchet and turns the edge of a knife. 

 In the deep holes made by the birds 

 the sunlight and air are excluded, and 

 perhaps the caustic action of the birds' 

 dung keeps an open sore which the fly 

 maggots soon convert into a rotting 

 mass. When one considers the great 

 numbers of insects which are dependant 

 upon this cactus it is not a little remark- 

 able that their existence should depend 

 for the most part, if not entirel}', upon 

 the operation of a bird. 



I made my first discovery of this 

 fauna upon Christmas day, and being 

 unable to complete m.y examination in 

 one afternoon I took home with me a 

 part of the disintegrated contents ot the 

 rotten spot which formed a hollow that 

 would hold perhaps a half a peck. The 

 next day I revisited this cactus and 

 brought home with me more of the 

 rotten contents, and although I have 

 spent one whole day and two half days 

 in examining this material and picking 

 out the insects in my room [ have not 

 yet finished. Of the many thousands 

 of larvae I have secured and jjreserved 

 a good series. I do not think that in 

 all my experience I have ever found so 

 many difl'erent species of Coleoptera in 

 one confined space, and as I have prac- 

 tically examined but a single cavity 

 there is no knowing how many more 

 species remain to be discovered. I 

 have noted 30 distinct species of Coleop- 

 tera upon a superficial examination and 

 I know that there are several others 

 overlooked in the mass. 



Tucson, Ar., Jan. 3, 1S97. 1 

 Since I last wrote I have been follow- | 

 ing up the insect fauna of the Giant I 

 cactus. These plants grow only on the ' 

 rocky hillsides, and although there are 1 

 many of them in the aggregate they are 

 generally a long way apart, and it 

 requires much climbing over rocks to 

 reach tliem. Sometimes there is a 

 family of them together, but they are 

 more often many rods apart. The i 

 trouble is to find one in good condition ! 

 for insects. I find many of them pros- 1 

 trated either by the prospectors search- ] 

 ing for ores or by the wind but not one j 

 in several square miles is in the right I 

 condition, and I believe it takes a year ] 

 for them to rot or dry up. Most often ' 

 thev are too old, and inside the split and ' 

 hardened skm is only a mass of black 

 dust and a arreat bundle of wooden rods. 1 

 I have sifted these dry interior contents ' 

 but found only the elytra of Cactoplia- ' 

 gus validus of which I have full grown I 

 larvae from the heart of the cactus. I 

 will come upon the living imago some 

 day. I found lately a huge trunk, cut 

 down and partly rotten and filled with 

 countless myriads of Staphj'linidae, I 

 large and small, the little Histeridae, I 

 the Hydrophilidae, large and small, i 

 with Pseudorcorpions and flies by the j 

 millions. There will be fifty species { 

 at least of this cactus fauna ; unfortu- | 

 nately some of them are extremely rare 

 or hard to find in the swarming mass \ 

 of small Staphylinidae. The most ' 

 difficult to secure are the minute and j 

 very rare Pselaphids, Scydmaenids, 

 Trichopterj'gids etc. These are found . 

 in tiie half di\' paits on tiic edges of 



