198 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
the outer joints larger, forming an open or compact club. All the 
tarsi are 5-jointed, the first and fourth joints small, and all but the 
fifth bearing a membranous appendage. ‘They range in size from 
about 5 to 15 mm. 
The larvae are adapted to crawling and gnawing in the burrows 
of wood-boring insects, where they are usually found. They are soft- 
bodied, elongate, parallel-sided or fusiform in shape, frequently 
highly colored, though often white and thin textured, and usually 
with ambulatory lobes well developed; they have five-jointed legs and 
often chitinized paired or pronged armature on the ninth abdominal 
segment. The spiracles are annular or pseudoannular, the head is ex- 
tended, clypeus and labrum are present, the mandibles are of simple 
type, the ventral mouth parts are not retracted, and the gula is dis- 
tinct (Béving and Champlain, 57). 
The habits of these beneficial beetles are fairly well known, and the 
records of the Division of Forest Insect Investigations were well sum- 
marized by Boving and Champlain (457). 
Most species are quite restricted both as to the food they eat and the 
host plant in which they occur. Jlonophylla terminata (Say) and 
Tarsotenus univittatus (Rossi) are predaceous on bostrichids, lyctids, 
and ptinids in dry, dead wood. Cymatodera bicolor (Say), C. in- 
ornata (Say), and Chariessa pilosa (Forst.) feed on wood borers, prin- 
cipally of the familes Cerambycidae and Buprestidae in recently dead 
or dying trees. They follow up the larval mines of these borers and 
after feeding on one larva search out and destroy another. In cages 
under artificial conditions some of these forms have been fed many 
times their weight in wood-boring larvae. Certain species, typically 
illustrated by Neichnea laticornis (Say), are predators within the egg 
tunnels of scolytids, where they feed on the eggs, young larvae, and 
parent adults. They remain during their entire life in the egg gal- 
leries of their hosts, where they mature and finally pupate. 
Such forms as Thanasimus dubius (F.) and Enoclerus quadri- 
guttatus (Oliv.) are typical associates of the bark beetles Dendroctonus 
and /ps in dying pine trees. The adults appear on the infested trees 
coincidentally with the bark beetles, which they catch and devour in 
great numbers. Their eggs are laid in the bark, and the larvae de- 
velop under the bark with the scolytid broods on which they feed. On 
maturing, the larvae pupate in the bark, or, with some species, in the 
ground at the base of the tree. The feeding habits of the adults are 
very characteristic and were described by Boving and Champlain 
(51, p. 624) as follows: 
* * * Sometimes they will attack insects much larger than themselves. 
In the usual method of attack the Clerid remains motionless until a wandering 
Scolytoid or some other insect approaches close enough. Then running with 
a rapidity that resembles a leap, it seizes the prey. Grasping it with the front 
and middle pair of legs and holding on to the bark by the hind pair, sometimes 
balanced by the tip of the abdomen against the bark, it proceeds to feed. With 
its strong jaws it breaks the chitin or separates the segments and feeds upon the 
soft tissue and viscera within. 
One of the early attempts by entomologists to use beneficial insects 
for the control of destructive species, was an experiment conducted by 
Hopkins (230) in 1892 with Thanasimus formicarius (1.), a Euro- 
pean clerid beetle, closely allied to 7. dubzus. At that time a wide- 
spread and destructive outbreak of the southern pine beetle was killing 
