288 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loi 



smooth. Unfortunately, only large fragments of these tubes were 

 found after digging up the cells. However, the larvae kept alive in 

 salve boxes quickly constructed new ones. 



The biology of Peltotrupes youngi is particularly interesting because 

 of its numerous differences from the known biology of beetles in the 

 closely related genus Geotrwpes. The major differences are in the 

 larval food and the loose manner it is placed in the cell, the use the 

 larva makes of its own fecal material, and in the opening and depth 

 of the burrows. 



The larva, previously described (Howden, 1952), exhibits several 

 interesting morphological peculiarities. The head capsule (pi. 9, 

 fig. 3) is asjmametrical, similar to the North American Geotrwpes, but 

 the third (terminal) antennal segment (pi. 7, fig. 6), which is reduced 

 to a mere cap on the second segment, is quite different. However, 

 the mandibles (pi. 9, figs. 4, 6), maxillae, and hypopharynx (pi. 9, 

 fig. 5) do not show any noteworthy departure from those of Geotrupes. 

 The glossa is not emarginate in youngi as it is in most Geotrupes. 

 The presence on the epipharynx (pi. 9, fig. 1) of 25 or more chaetae on 

 each chaetoparia and the shape of the endoskeletal figure of the anal 

 lobes (pi. 9, fig. 2) are both quite distinctive for youngi. 



Metathoracic legs are reduced in the same way as in Geotrupes. 

 All legs lack claws, but are terminated by several long stiff setae with 

 tuberculate bases. One quite distinctive characteristic is the general 

 body shape of youngi (pi. 11, fig. 1) with the head and thorax small 

 in proportion to the tremendously swollen abdomen. 



The egg of Peltotrupes youngi is yellowish white, almost oval, 

 slightly longer at one end than the other. Length 4.6 to 4.7 mm., 

 greatest width 3.0 to 3.5 mm. 



Maximum width of larval head capsules: First instar 2.5 mm.; 

 second instar 3.5 to 3.7 mm.; third instar 4.4 to 4.7 mm. 



Genus Mycotrupes LeConte 



Mycotrupes LeConte, 1866, pp. 381-382.— Horn, 1868, p. 314. — Blanchard, 1888, 

 p. 109.— Bradley, 1944, p. 112.— Olson, Hubbell, and Howden, 1954, pp. 1-59. 



Genotype: Geotrupes retusus LeConte, by monotype, in LeConte, 

 1866. 

 Generic limitations: Given by LeConte (1866, p. 381): 



The elytra are broadly ovate, very convex, connate and destitute of striae; the 

 clypeus is semicircular, with the lobes before the eyes large and rounded; the 

 front in the male is armed with a short horn or acute tubercle, which in the female 

 is reduced to a feeble elevation; the prothorax of the male is flattened and 

 declivous before the middle, and longitudinally broadly excavated, thus producing 

 a transverse somewhat lunate elevation about the middle; in the female a slight 

 dorsal channel is seen, and a feebly impressed fovea each side, halfway between 



