32 Transactions.— Zoology. 



uncommon in that region. The waxy tests are very small 

 and inconspicuous. 



The finding of the adult female enclosed in the waxy mass 

 formed by the female of the second stage was a surprise to 

 me, being a distinct departure from the normal condition of 

 things, especially in the group Monophlchida . It affords a 

 good instance of the necessity, as I take it, of thorough ex- 

 amination of all stages before any absolute certainty can be 

 arrived at, even as to the generic position of an insect. What- 

 ever may be the rule amongst other orders and families of 

 insects, Coccids present this difiiculty to students : that one 

 must be prepared at any time to find very distinct departures 

 from generic, or even group, types, and to consider any cha- 

 racter whatsoever as elastic and variable. Thus, for example, 

 in the Dactylopldce, the insect described in my last paper 

 under the name D. ohtectus departs entirely from the generic 

 type in employing a portion of the plant it lives on as a 

 shelter or "scale" for the adult female. So, again, in the 

 MonojMehidcc, no genus or species has been reported hitherto 

 in which the adult female is not, at least before gestation, 

 free and active, or only covered with loose cotton. Colostoma 

 assimile departs altogether from the types of the group and 

 the genus in remaining under the thick waxy test in its adult 

 state ; and the variation is emphasized, so to speak, by the 

 absence of the feet. The cho.racters, however, of the larva 

 and of the second stage being so clearly those of the genus 

 Go&lostoma, and the rostrum and mentum of the adult being 

 entirely absent, I have no hesitation in retaining the insect in 

 that genus despite the form of the antenna ; and, indeed, this 

 may be looked on as merely atrophied. 



The deep ca^dty made by this species iu the wood of its 

 tree, and its usual position in the axils of the twigs, make it 

 resemble Xylococcus filifcrus, Low (Verb, der zool.-bot. 

 Gesellschaft, Wien, 1882), which insect also has a small cover- 

 ing of wax, and a very long slender filament protruding from 

 the abdominal extremit3^ But the presence in Xylococcus of 

 a very distinct rostrum (which, indeed, seems to be the only 

 member preserved by the adult female) clearly distinguishes 

 that genus from Ccelostoma ; and, indeed, the forms of the 

 larva and of the second stage are also quite different. 



The late Dr. Low, whose death a few months ago deprived 

 entomology of one of its brightest ornaments, devoted some 

 remarks in his description of Xylococcus filiferus to the ques- 

 tion of the manner in which that Coccid managed to produce 

 a deep cavity in the wood of its food-plant, Tilia europcea. 

 He was, however, unable to give any other explanation than 

 that it proceeded " by a most peculiar kind of suction, and 

 besides by a certain influence which these insects exercise on 



