AND OX THE VIVIPAROUS HABIT OF OTHER DIPTERA. 453 



strong spines with which the abdomen is thickly studded; as 

 I shall show later, by observations on other species, this is an 

 unusually large number (Figs. 2, 3, 9). The plates on the- 

 abdomen have their spines opposed in direction to that of the 

 point of the hook, and, in conjunction with the fact that the 

 insect is viviparous, afford a very remarkable problem ; as I 

 said before,* the question arises, " To what use does an insect 

 put an ovipositor when that insect does not lay eggs ? " 



I can now answer that question ; but the subject is not a 

 pleasant one, and it seems one of the cruellest in Nature. 



It has been recorded by Schiner f that the rly has been bred 

 from the pupae of larvae found in the caterpillars of Sphinx 

 pirastri (which, unless that is a misprint for "pinasfoH" the 

 pine hawk moth, is a foreign species), Liparis (= Porthesia) chry- 

 sorrhaea, L. (brown-tail moth), Leucoma salicis, L. (white satin 

 moth), and Pieris brassica, L. (large w^hite butterfly). In the 

 cabinet of the British Museum (Natural History) is a small 

 caterpillar of L. salicis, L., and another of fiombyx neustria, L. 

 (lackey moth), from which this fly has been bred in Britain. 

 Putting together the points observed with the microscope — the 

 viviparous condition, the piercing hooks and opposed serrations — 

 with the records of Schiner and the Museum, it can be under- 

 stood that living larvae are introduced into the unfortunate 

 caterpillar, the fly making an aperture for their entrance by 

 forcing the hook into its victim, the necessary purchase being 

 obtained from the grip of the plates on the caterrjillar, giving 

 a hold in an opposite direction to the force expended on the 

 penetrating hook. Well might Tennyson sing of : — 



Who trusted God was love indeed, 

 And love Creation's final law, 

 Though Nature, red in tooth and claw 



With rapine, shrieked against his creed. + 



Putting the cruelty aside, the Lepidoptera preyed on are 



* Jour. R. Mlp. Soc, 190S, pp. 421-2. 

 f Die Fliegen, vol. i. p. 489. 

 \ In Memoriam, lvi. 

 Jourx. Q. M. 0., Series II. — No. 65. 34 



