56 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Tracheal Ramification^ in Dytiscus. — Alexis Koppen (Zool. 
Anzeig., 1921, 52 , 132-9, 4 figs.). Some precise details of the extra- 
ordinarily fine ramification of the tracheae, e.g. on the gizzard and the 
crop of this water-beetle. There is what may be called a capillary 
network. The state of affairs in the fat-body is also described, and a 
striking figure is given of the inter-penetrating branching on the 
stomatogastric nerve. Anastomoses were only seen in a few cases in 
the spiral tracheae of the hind-gut. There are no anastomoses among 
the capillary ramifications. J. A. T. 
Olfactory Organs of Wasps and Bees. — R. Vogel (Zool. Anzeig ., 
1921, 53 , 20-28, 4 figs.). A description of sensory cones (sensilla 
basiconica), sensory plates (sensilla placodea), and sensory hairs (sensilla 
trichodea olfactoria) in wasps and bees. Each type includes a group of 
very small sensory cells with distal processes. These cells vary in 
number in the three types, respectively, 30-40, 12-18, 5-10 ; they are 
innervated by very delicate nerve-fibres ; the distal processes always 
contain near their outer ends a row of characteristic granules. The 
queen-bee has about 2,000 olfactory plates on each antenna, the worker 
about 6,000, and the drone about 30,000 ; and each placode has about 
16 sensory cells. The drones are obviously well equipped for finding a 
queen. Cones and hairs occur on the antennae of Mvriopods ; the cones 
may be derived from the hairs by increase in the chitinous portion and 
in the number of sensory cells. By shortening of the cones plates may 
arise. J. A. T. 
Nymph of Gryllus campestris with Three Cerci. — J. Regen 
(Zool. Anzeig ., 1921, 52 , 189-90, 1 fig.). Among about 2,000 larvae 
of this cricket there was a nymph with three cerci — two being 
asymmetrically disposed on the right side of the ovipositor, one on the 
left side. The specimen died at the last moult, and two others which 
showed a hint of a third cercus also failed to reach the imago stage. 
5. Arachnida. 
Reproduction and Sex in Ornithodorus moubata. — N. Cunliffe 
■(. Parasitology , 1921, 13 , 327-47, 1 ph, '5 figs.). Copulation may occur 
between individuals of two species, O. moubata and O. savignyi, and the 
stimulus of coition may induce oviposition. But the eggs are non- 
fertile. There is no evidence of parthenogenesis in O. moubata. There 
is no ecdysis after reaching maturity. An increase in temperature from 
8° C. to 22° C. doubles the rate of oviposition, decreases the fertility of 
the eggs by 30 p.c., reduces the longevity of the female tick from 715 
to 397 days, i.e. by 40 p.c. ; and apparently halves the period required 
for metamorphosis, under laboratory conditions. At 37° C., under 
laboratory conditions, reproduction is inhibited, and the longevity of 
the female is reduced by 80 p.c. An individual may undergo from four 
to eight ecdyses before reaching maturity. The great majority of the 
males appear after the fifth ecdysis, and the females about equally after 
the fifth and sixth ecdyses. Engorgement may take place one or two 
days after emergence, at any stage, the average time required being 
