History and Habits of Pityogenes. 51 
normal, these will be spaced evenly at a distance of from 
1 mm. to 2 mm. from each other as shown in galleries 
a, b, c, in Fig. 20. In this way, if surrounding conditions 
are right, each larva is insured an adequate supply of food 
at the expense of the least exertion on the part of the 
mother. However, the fact that egg galleries either from 
the same or from different brood chambers often run closely 
parallel to each other, furnishes a factor which frequently 
alters greatly the typical arrangement. 
A eareful study of Fig. 20 will make this evident. Gal- 
leries a, b, and ¢, are spaced far enough apart that the typical 
and ideal arrangement of the egg niches is not affected, 
The other galleries, however, all run more or less closely 
parallel to each other and the result is apparent. Evidently 
galleries d and e were both started at about the same time 
and earlier than gallery f. The females in galleries d and 
e evidently being aware of the proximity of the two gal- 
leries, instinctively placed their eggs at greater distances. 
Apparently they extended their burrows at about the same 
rate. When female e had extended her burrow about two- 
thirds of its entire distance it apparently began to parallel 
gallery g coming from the opposite direction. Both females 
e and g then immediately began placing all of their eggs on 
the side of the burrow farthest from the other burrow and 
female d acted in a similar manner as if it were aware of 
the changed tactics of female e. Female e exhausted her 
supply of eggs sooner than did female d and ceased burrow- 
ing, whereupon the latter immediately began placing her 
eggs upon both sides of the gallery again. Gallery f was 
apparently started slighly later then d and e and, being 
aware of the nearness of the other burrow, female f from 
the start placed all of her eggs upon the side farthest from 
gallery e. The arrangement of the egg niches in galleries 
-h and 7 is explained in a similar manner as they apparently 
started later than galleries f and g 
Another interesting fact to be aah ed with regard to 
the spacing of the egg niches is illustrated in Fig. 21. 
Very often the egg niches in the first two-thirds of the 
