194 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



by Mr. Rohwer as Dianthidium arizonicum the following notes 

 are worth recording. 



This nest was a nearly globular mass of resin and small pebbles 

 (granite sand), attached to a twig about one-half inch in diam- 

 eter and at the time received contained one larva and four prepupal 

 larvae in cocoons. It is reproduced, about natural size, on 

 plate XV, figs. 1 and 2. 



The prepupal larva is yellowish white, about 12 mm. long, 

 constricted ventrally and expanded dorsally to form a U. The 

 circumference of the body anteriorly is less than the circumference 

 posteriorly which makes a somewhat pear-shaped outline. The 

 greatest dorsad-ventrad diameter is 3.75 mm., at about two- 

 thirds the body length beyond the head. The head is entirely 

 pale; 1 mm. broad and 1.2 mm. high; frons triangular, not dis- 

 tinct; anterior margin of labrum finely crenulate, the dorsal and 

 lateral margins arched (see fig. 36); mandibles small and com- 

 pletely covered by the exterior angles of the labrum; maxillae 

 and labium spined; antenna, situated against frontal epicranial 

 suture about length of labrum above dorsal articulation of man- 

 dible and consists of a large pure white, membraneous circle 

 from which a small yellowish white cone projects (see fig. 3c). 



The cocoon is a thin, transparent pale brown, oval, 8.5 mm. 

 long by 4.5 mm. broad, with one end darker, thicker and with a 

 distinct although small mamma. The mamma has a small 

 opening apically, basally there is a partition separating it from 

 the interior of the cocoon (as shown in fig. 3a). The cocoons 

 are completely buried in the nest mass and not protruding from, 

 or exposed at, the surface, nor are they smaller than the cell to 

 which their walls adhere. 



The following table summarizes some of the points known 

 concerning the biology of this and the three other Neartic species 

 of Dianthidium whose nests have been described. The data 

 concerning D. texanum was taken from Melander (Biol. Bull., 

 vol. 3, No. 112. pp. 27-34); that concerning D. consimile from 

 Davidson (Ent. News, vol. 7, 1896. pp. 22-25) and that concerning 

 D. cressoni from Cockerell (Bull. Am. Mus. Nat. Hist., vol. 22, 

 1906, pp. 444, 445). 



EXPLANATION OF PLATE. 



Fig. 1. Entire nest. 



Fig. 2. Nest broken open showing, cocoons, and cell from which 

 cocoon has been removed. 



Fig. 3. a, Section of anterior end of cocoon, b, Labrum of larva. 

 c, Antenna and portion of head of larva showing, dorsal articulation of 

 mandible (dam) and frontal epicranial suture f/es). 



