149 



Reply— * » * The specimens last sent are the large Texan Digger Wasp or 

 Horuet (Pejysis formosa), oue of the largest and most showy of the fossorlal or sand 

 wasps. It is commonly known as the Tarantula-killer and is reported to attack that 

 enormous spider, Myyale hentzii, stinging it and inserting an egg in its body, after 

 which the spider is introduced into a hole or nest in the sand some 5 inches deep. 

 The wasps emerge in June and are common until Fall. It is a southwestern species 

 but occurs as far north and east as central Kansas at least. There is a full illustrated 

 account of it in Vol. I of the old American Entomologist. * * *. — [October 2, 1889.] 



Abundance of Datana angusii. 



I wish to call the attention of the Department to a new and very destructive spe- 

 cies of caterpillar — at least new to us. As nearly as I can ascertain, this caterpillar 

 made its appearance here about three years ago, but perhaps longer. It prefers for 

 its abode hickory and walnut shade trees in pasture fields, meadows, and grain fields ; 

 and I believe also apple trees. When they have once taken possession of a tree they 

 never quit it so long as the semblance of a green leaf remains ui^on that tree. They 

 leave not a skeleton leaf, as does the well-known orchard caterpillar. The petiole and 

 a portion of the axis or midvein is all that remains to show that a leaf once existed 

 there, whether simple or compound. I have been observing this pest with a view to 

 ascertain some of its characteristics and habits, and experimenting as to the most 

 effective means for its destruction. It is distinct from the web caterpillar, in that it is 

 large and more voracious. It does not spin a web, nor does it draw the leaves together, 

 but devours them bodily, net, veins, and all, except as above stated, the jjetiole and 

 the heavier portion of the axis. 



General Appearance. — In color it is dark purple, with four well marked white lines 

 on each side ; the lowest being the heaviest, and the second from below being light- 

 est, while the two uppermost lines are of about uniform size, and about half as wide 

 as the lowest. Its head is black, and armed with powerful mandibles. It is partially 

 covered with thin rows of white hair. 



Size when full grown. — When full grown it is probably 6 centimeters in length and 

 6 millimeters in diameter. Its body is now a little darker and its hair a little longer 

 and whiter than in the young of 2 centimeters length. 



Rahils observed in fteding and Manner of Repose. — These caterpillars travel up the 

 tree from the ground, single file, each oue leaving a thread behind it, which every 

 other carefully follows doing likewise uiitil all camp upon the same leaf until it is 

 literally covered, and which they do not leave until there remains only a melancholy 

 ruin, not having the semblance of a leaf, when they turn and follow back the thread 

 to a point a foot or often several feet above the ground, where they pile upon each 

 otber like bees for repose, to the number of many thousands, and the bulk of a pint 

 or more. They hold fast b}^ the middle^, turning the two extremities out. Several 

 such bunches are often seen upon the body of the same tree. Just beneath the limb 

 as it leaves the trunk of the tree is a favorite resting place of these very peculiar or- 

 ganisms. When the leaves of one branch are devoured (and they usually select the 

 lowest branches first), one of them strikes out in a new direction, laying his thread, 

 which all the rest follow till they arrive in pastures new upon another branch; and 

 so they go from branch to branch till not the semblance of a green leaf remains upon 

 the tree. They have now completed their work — verified the teaching of Malthus. 

 They retire to their camps for repose, where they perish for lack of more leaves to 

 devour. Here their remains are bound together by an almost imperceptible fiber or 

 thread, and are not dislodged by the peltings of hail or by winter storms. The crops 

 of several years past are distinctly seen upon the trunks of the trees they have 

 stripped of their foliage and of their glory. 



These caterpillars are rapidly increasing in numbers. In an adjoining countj- an 

 entire orchard is reported as destitute of leaves as in midwinter. I have seen no ac- 

 count of this new pest; probably it has not been reported. I have never seen this 



