382 



NATURAL HISTORY OF ARTHROPODS. 



species with brownish legs and antennse, and about 0.2 of an inch long, is often very- 

 abundant in flowers of the wild morning-glory ( Calystegia septum) in the northeastern 

 United States. 



Separated from the species of the preceding family by their slender tarsi, of which 

 the first joint is short, are the Teogositid.e. Of this family there are two groups 

 readily distinguished by their form. The species of the first group are elongate insects 

 with the prothorax narrowed behind. Trogosita mauritanica is a cosmopolitan 

 species of this group. It is deep brown, flattened, and about 0.4 of an inch long. The 

 species of Trogosita are often found under decaying bark, but certain of them have 

 proved to be very injurious to grain, and to other articles of commerce. Thymalus 

 fulgidus is a common representative of the second group of the Tro- 

 gositidse, which contains oval species. This is a nearly round, some- 

 what flattened species, about 0.2 of an inch long, which abounds on 

 Polyporus betulinus, a large, white fungus that is parasitic on trunks 

 of dead birch trees. The beetle is a slightly shining bronze color, and 

 is both punctate and pubescent. Its larva is 0.3 to 0.4 of an inch long, 

 somewhat flattened, and has the anal extremity armed with two parallel, 

 acute, corneous processes, along the sides of which are a few sharp, short 

 branches. The larva, which is of a hyaline white with a yellowish head, has five ocelli 

 on each side of the head. The larvfe generally destroy the tough tissue of the above- 

 mentioned fungus during the early spring, in the eastern United States, and pupate in 

 the remnants of their food-plant, the beetles emerging during the summer. 



A considerable number of small beetles that are, for the most part, round, hard, 

 and seed-like in appearance, and generally live upon decaying animal or vegetable 

 matter, are united in the family Histbeid^. They differ systematically from the Ni- 



ITIG. 446. — Tro- 

 gosita Ttiauri- 

 tanlca. 



Fig. 447. — HUtcr arouatus. 



Fig. 448. — Hister bimacwlatus. PiG. 449. — Onthrophilws altematus. 



tidulidsB in having geniculate antenuEe. Most of the Histeridse are black, a few have 

 red spots, and a small number are metallic in coloration ; all their tibiffi are usually 

 dilated ; the elytra are truncate behind, leaving two abdominal segments exposed; the 

 upper surface is striate, the position and nature of the strife being generally of value 

 as specific characters. The larv88 of the Histeridae are elongated, with corneous head 

 and prothorax, and have no ocelli. Some species of this family inhabit ants' nests, a 

 few live under bark. Ulster helluo is known to eat larvse of Agelastica alni, and U. 

 pustulosus drags the larvte of Agrotis, a noctuid moth, from their holes and devours 

 them, in company with others of its species that hasten to the repast. 



In the species of Saprmus the head is bent downward and retracted ; the protho- 

 rax is truncate anteriorly, and has cavities at its side for the reception of the antennae, 

 which are inserted beneath the front. There are nearly sixty North American species 



