948 SUMMARY or CURRENT RESEARCHES RELATING TO 



membranes inclose three air-spaces which act as resonators, and are 

 formed by the suppression of visceral and muscular elements. These 

 essential organs are covered and protected by stout chitinous plates — a pair 

 projecting forwards over the sclerous rattle membranes, and another pair 

 arising externally to the legs in the mesothorax, and extending backwards 

 to cover the air-chambers. The modifications are merely suggested in the 

 female. A series of experiments is described which point clearly to the 

 functions of the various organs as assigned to them by Mr. Lucas, and 

 dissections and plates accompany the paper. 



Structure of the Head of Blow-fly Larva.* — Prof. B. T. Lowne has 

 come to the conclusion that embryology shows the futility of discussion 

 with regard to the segmentation of the head in insects ; he compares them 

 with those which have been held with regard to the vertebrate skull ; 

 no segmentation occurs in the pre-oral region, and the head consists of 

 an unsegmented pre-oral cap, developed from the cephalic fold, of two 

 lateral procephalic lobes, and of three post-oral segments with their three 

 pairs of lateral appendages. The antennse are developed from the non- 

 segmented pre-oral region, and, like the eyes, have no homologies with 

 limbs. " A comparison between these structures and the post-oral appendages 

 has no more basis in their developmental history than a comparison of the 

 trabeculae cranii with the ribs, or of the sense corpuscles of a vertebrate 

 with its limbs." Mr. Lowne is of opinion that the whole exterior of the 

 proboscis, except the labium, represents the galeae and stipes of the maxillae, 

 while the edges of the labrum and its apodemes represent the lacinia ; if this 

 view be correct there is nothing abnormal in the position of the maxillary 

 palpi. 



Sexual Generation of Chermes.f — Dr. F. Blochmann has elucidated an 

 obscure point in the life-history of Chermes in discovering the sexual 

 generation. The observations of Eatzeburg, Leuckart, and others had 

 long since demonstrated (a) that a parthenogenetic, wingless generation 

 passed the winter and deposited eggs at the base of the buds of the pine, 

 (&) that their progeny developed in the galls and emerged in early summer 

 as a parthenogenetic winged brood, and (c) that these produced a small 

 yellowish wingless generation. It was supposed, direct evidence not being 

 forthcoming, that the latter became the parthenogenetic winter generation (a) 

 above referred to. 



This Blochmann has shown to be a mistaken inference. The yellow 

 coloured brood are sexual. Males and females are readily distinguishable, 

 the former by the brown colour of the posterior portion of the body and 

 by their very active habit. They possess two conspicuous testes and a penis 

 beset with barbs. The females are yellow and not brown posteriorly, and 

 of sluggish habit. They possess a single oviduct, two accessory glands, 

 and a receptaculum seminis full of sperms. Both sexes exhibit a well- 

 developed proboscis and alimentary canal. 



After impregnation, the females hide at the bases of the needles on the 

 somewhat thicker branches. There they lay a few eggs and die. Prom 

 these fertilized ova the winter (a) parthenogenetic forms result. These 

 are found at the bases of the buds from October onwards. The entire 

 life-history thus closely resembles that of Phylloxera. 



♦ Journ. Quek. Micr. Club, iii. (1887) pp. 120-4. 

 t Biol. Centralbl., vii. (1887) pp. 417-20. 



