ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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special entrance tube. This may in section be seen to be constricted 
in several places by discs, which leave only sufficient space for the 
passing of one bee at a time. If beaten back, therefore, from the first, 
they have still the chance of successively holding the inner ones. These 
constrictions and the sealing up are evidently adopted by the insects as 
a means of defence against their enemies. At nightfall, the orifice 
which admits of ingress and egress during the day is sealed completely 
over, only all but imperceptible orifices being left in the closing sheet 
of wax. Near daybreak this safeguard is regularly removed. This bee 
has no sting, and hence, we may suppose, the careful means of defence 
which it adopts. 
Another species of Trigona, which has likewise no sting, is very 
pugnacious, and attacks persons coming near with a buzz and a hum 
similar to that of the common honey-bee. It fixes itself in the hair and 
produces a tickling feeling, which quickly induces a sensation of fear ; 
“ even when its character is known the attack (almost unconsciously) 
causes the intruder to retreat.” 
Self-mutilation in Larvae of Phryganidae.*— Grafin M. v. Linden 
robbed a larva of Limnophilus of its covering. The creature crept about 
from stem to stem without seeming to find anything suitable for a new 
case. During the night of the second day it seems to have removed the 
tarsal joints from its first right and second left legs. It was not possible 
to say that an enemy had done it, for none was present. 
Systematic Position of Strepsiptera.f — Prof. N. Nassonov discusses 
the systematic position of the Strepsiptera as indicated by the facts of 
postembryonic development and of anatomy. He has chiefly studied Xenops 
Bossii. The mouth-parts are found to be formed at first of two simple 
lamellae, that is of an upper and a lower lip which bound the mouth ; in 
the cavity of the mouth there is but a single pair of appendages, the 
“ upper jaws,” which are arranged like those of Campodea. The “ lower 
jaws ” are completely absent. The author does not agree with Siebold 
in stating that there is a difference between the male and female apodal 
parasitic larvae, for he finds that the sexual distinctions only appear 
after metamorphosis. An account is given of the changes undergone by 
the two sexes. They may be summed up by saying that, while the male 
passes through a complete external and internal metamorphosis, accom- 
panied by profound modifications of the organization of the larva, the 
female undergoes much less marked changes, and the organization of 
the adult female, sexual organs excepted, differs very little from that of 
the larval stage. 
The chief points by which the Strepsiptera are distinguished from 
other Insects are : (1) the absence of posterior and inferior lips, the very 
feeble development of the “ lower jaws ” in the males, and their com- 
plete absence in the females ; (2) the orifice of the mouth is at a distance 
comparatively considerable from the parts of the mouth ; (3) the anterior 
pair of wings and the appendages of the male are specially modified ; 
(4) the central nervous system is formed of three ganglia ; (5) the 
female has no mid-gut ; (6) there are no Malpighian vessels or cutane- 
* Biol. Centralbl., xiii. (1893) pp. 81-3. 
f Congres Internat. de Zool., II. i. (1892) pp. 174-84. 
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