Junk, 1889. 
WILD BEES. 
127 
But before entering into a discussion of these colours, it is 
better to speak of the attacks of the Nomadce on the Andrence. 
It is generally stated that they are allowed by the Andrence 
to enter their burrows “without let or hindrance,” and, in a 
way, this would seem to be correct. But it should be noticed 
that these parasites are extremely cautions in entering a 
burrow, hovering for a time at the mouth, or often entering 
a little way, and then flying off to another ; without doubt, such 
behaviour is due to their fear of encountering the Andrena , if 
at home. On the other hand, if the Andrena returns when 
the parasite is within, as must sometimes happen, she waits 
until the latter has flown off: so that both, it would seem, 
equally avoid an encounter. 
Another reason for this belief is found in the fact that 
(except of course when recently emerged from the pupa stage), 
the Nomadce do not rest at night or in bad weather in the 
burrows of the Andrence : but above the surface of the 
ground. 
Shuckard, in his “ British Bees,” noticed that while a 
colony of bees would continue to abound in about equal 
numbers year by year, their parasites would be abundant one 
year and very rare another. He did not however see the 
cause of this, and I am not aware that it has been mentioned 
by any of our other liymenopterists. It is certainly because 
they are thus exposed to all weathers, that the great variation 
in their numbers in different seasons is due : while bad 
weather does not equally affect the Andrena, which is sheltered 
in its burrow. 
Even the habit among parasitic bees of sleeping out 
seems hardly to have been observed, though other genera 
besides Nomada do so—for instance, Melecta, which I have 
frequently found so circumstanced on the wettest days, and 
Epeolus has been noticed by Linnaeus as attaching itself 
to the beak of the flower of Geranium Phceum. The Nomadce 
often choose as a place of rest the flower heads of various 
grasses; attaching themselves to one of these by the 
mandibles, they draw up their legs close to the sides of the 
body, fold their wings over tbe back, and extend their 
antennae straight out in front. In this position they are in 
perfect harmony in form and colour with the flowers or seeds 
of grass, and very difficult to detect, even more so—allowing 
for their smaller size—than is the butterfly, Thanaos tapes, 
when at rest in the same situation. With regard to this 
butterfly, it is solely from its habit of resting on grass heads 
and the blossoms of rushes that it sleeps on these with wings 
deflexed like a moth, whereby a more perfect concealment is 
