32 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the loaves of belladonna, mangolds, beet, and henbane. It causes a 

 blistered appearance on the leaves and they soon wither. Hibernation 

 occurs in the pupal condition about two inches below the surface of the 

 soil. The eggs are laid superficially on the back of the leaf in groups 

 of parallel rows. The incubation period is about live days. The larvae 

 feed uninterruptedly and complete their metamorphosis in about 10 days. 

 The average period for a complete life-cycle is about ?»G days. There 

 may be three broods in the season. Two closely related species, P. 

 bicolor and P. nigritarsis attack common weeds like the dock, and their 

 life-histories resemble those of P. hyoscyami. Experiments showed 

 that mangold-reared adults would not oviposit on belladonna, and vice 

 versa. Some natural control is secured by the parasitism of two species 

 of Braconids, on one or both of which a Proctotrypid is probably 

 hyper-parasitic. 



S- Arachnida. 



Nests of Pseudoscorpions.* — H. Wallis Kew has made a careful 

 study of these interesting structures. They are made in part or 

 wholly from silk produced by the pseudoscorpions, which enclose -them- 

 selves in the nests for moulting, for brood purposes, and in some cases 

 for hibernation. Such nests are closed cells of spun-tissue with or 

 without an external covering of extraneous materials. The internal 

 spun-tissue is thick and dense, almost like silk-paper. It is composed 

 of innumerable threads crossed and re-crossed, and coalesced in irregular 

 confusion and without interspaces. 



The material is secreted by glands in the cephalothorax whose ducts 

 traverse the cheliceras and open at the tips of the branches of the galea, 

 or on or near the margin of a tubercle which replaces that structure in 

 some groups. Spinning is done with the chelicerte, the animal gradually 

 imprisoning itself. The construction of an external framework is the 

 first part of the task, silk threads forming an open irregular mesh-work 

 to which extraneous material is usually attached. 



The silk is drawn from the galea or tubercle in several separate 

 viscid very fine threads, which remain separate or coalesce, all those 

 from each galea or tubercle sometimes forming a single thread. In 

 spinning there are continuous forward and backward movments of the 

 body and lateral movements of the chelicerae. 



During the earlier parts of the work, when attachments are being 

 made from place to place, the threads usually coalesce, and since they 

 fuse at once, either before or after coalescing with other threads or 

 objects, the irregular mesh-work soon results. Afterwards the animal 

 settles down to long-continued spinning, and silk is rapidly brushed on 

 to the interior, first in one place and then in another. The threads 

 now usually fuse separately, being appbed in more or less parallel 

 series of several side by side ; and when both galeae or tubercles are 

 used together, ten or twelve threads may be deposited at a time. The 

 animal continues thus to work at intervals for days or even weeks, till 

 the final dense tissue is at last produced over every part of the interior 



* Proc. Zool. Soc, 1914, pp. 93-111. 



