Field Studies of the Non-Social Wasps 409 
Bull. Conn. Geol. & Nat. Hist. Surv. 22: 676. 1916); 7. 
plesium nidifies in twigs; 7. leucotrichium builds in hol- 
low twigs of bamboo (Howes, Insect Behavior, p. 40. 
1919) ; 7. cinereohirtum builds nests in nail holes, spools, 
glass tubing, (Howes, Insect Behavior, p. 27. 1919); T. 
intrudens ‘‘hatched from the mud cells made by Para- 
pison rufipes (Wood, Insects ‘Abroad, p. 471); T. brevi- 
carinatus forms her nest beneath a palm leaf, and may 
cement together as many as twenty-five cells (Bodkin, 
Ent. Soc. Lond. 1917: 297-321, fide Williams) ; 7. elong- 
atum nests in bamboo twigs lying on the floor of a ra- 
vine (Williams, Phillippine Wasp Studies, p. 143. 1919) ; 
I’. pileatum uses ready-made cavities and makes mud 
partitions ; sometimes the mother digs her own tunnel in 
twigs. (Dutt, Mem. Dept. Agric. India 4: 201. 1912). 
With such a variety of methods of nesting within the 
Single genus, one sees in 7’. clavatum an indication of an 
unstable condition of the species. Lither all cell-like 
places are equally good for the development of the young 
of the species, or natural selection has been lax in elim- 
inating the individuals which chose the less favorable 
nest. 
But let me return to 7. clavatum as for the time the 
center of my study (fig. 53). The clay bank was an ex- 
ceptionally fine location, with the sheltering porch over- 
head, and facing the morning sun, and with foliage and a 
dozen old buildings near by to harbor spiders. So, with 
the additional advantage of having the male present to 
keep out the parasites, it would indeed have been sur- 
prising if this species had not gained a good foothold. 
The JT. clavatum made their appearance in the clay 
bank June 26, 1917, and were present throughout the 
Summer until late autumn without interruption, except- 
ing a short period late in July, that period probably be- 
