THE CHALCIDOID GENUS PERILAMPUS. 39 



REPRODUCTIVE CAPACITY. 



It is a well-known fact that insects which are subject to very high 

 mortality in their younger stages must have a liigh potential rate of 

 reproduction in order to offset this loss and still prevent the species 

 from becoming extinct; and conversely, we may say that insects 

 laying a great number of eggs must of necessity experience a very 

 high death rate or else they would in time increase beyond all bounds. 

 We have found by the dissection of adult female Perilampus that the 

 eggs are very numerous, the abdomen containing as high as 250 fully 

 developed eggs at one time. It is therefore apparent that in some 

 stage or stages before maturity many of the young die. As Peri- 

 lampus is eminently well fitted to withstand the vicissitudes encoun- 

 tered in its later existence, the logical place to find this high death 

 rate is during the planidium stage, while the tiny larva is wandering 

 about either within or outside the caterpillar in search of its host. 

 That this wandering habit of the younger, pre-eruciform stages of 

 parasitic larvae is accompanied by great mortality is well exemphfied 

 in the case of the Strepsiptera. Newport, in his ''History and 

 General Anatomy of Meloe and Its Affinities," ^ records tlie produc- 

 tion of more than 7,000 triungulins by a single female of the genus 

 Stylops. Pcrilamims is apparently not only subject to a considerable 

 mortality by reason of its wandering habit, but large numbers meet 

 their death through a failure to find a proper host within the cater- 

 pillar and through the operations of superparasitism after they do 

 find their host. 



Wliatever be the real method by which the planidium becomes 

 affixed to the caterpillar, the life history from this point on has been 

 worked out by actual observation in the laboratory, with an abun- 

 dance of material for study. 



DESCRIPTION OF PLANIDIUM OF PERILAMPUS HYALINUS. 



(Figs. 24, 25.) 



Length about 0.3 mm., depending on the amount of distension; 

 diameter at widest place about 0.06 mm. Shape obovate; composed 

 of 13 distinct segments or rings which are dark brown and heavily 

 chitinized, and which ''telescope" into each otlicr more or less. 



Head heavily margined, both laterally and posteriorly above, the 

 rim strongly emarginate or indented posteriorly, where it is also 

 strongly elevated in life and darker than other portions of the head. 

 Mandibles well developed, hook-shaped, situated in a buccal cavity, 

 and crossing at tips ; bases broad, with a rather large area for muscular 

 attacliment. Immediately back of the mandibles are two flattened, 

 heavily chitinized organs, which are probably homologous to the 



I Proceedings of the Liuneao Society of London, vol. 1, pp. 317-320, 368-370. 



