ON THE OCCURRENCE OF STEXOMALUS MUSCARUM 141 



2. The species is reported to have been bred from 

 the puparia of Musca, and the female is said to lay its eggs 

 on JZ/cj-aV/ larvae. 



3. All the hibernating examples which I have personally 

 examined prove to be females. 



4. Is the occurrence of this Chalcid with the Diptera 

 a fortuitous association to be explained simply on the 

 ground that different species have selected the same winter 

 quarters, or have we here an adaptation of habit on the part 

 of the Chalcid enabling the parasite to oviposit most 

 advantageously in the spring? There is evidently room for 

 an interesting piece of oncological research. To draw 

 attention to this, indeed, is one of the purposes of the 

 present note. The chief points to be ascertained are 

 how the Chalcid comes to its winter quarters, and what it 

 does after leaving them. 



5. The Chalcid parasites of household insects are 

 numerous. Of the single family Pteromalidae, within which 

 Stenonialns falls, there are seven or eight or possibly more 

 genera with such hosts. Some, like Spalangia, Latr. (on 

 Mused) and Cerocephala, Westw. (on Calandra), are easily 

 recognised ; but others, like Arthrolytus^ Thoms {Sitodrepa, 

 etc.), Dibraehys, Forst (various hosts), Pteromalus, Swed. 

 (Lepidoptera, etc.), are somewhat difficult to separate from 

 Stenomalus, Thoms. 



In the last-named genus the right mandible has four and the left 

 three teeth, the uppermost being broad ; the occipital foramen is 

 not margined ; the antennas are inserted above the base line of the 

 eyes in circular scrobes ; the gente are narrowed and very distinctly 

 convergent towards the mouth, while the clypeus bears a median 

 tooth in addition to the usual lateral lobes (see figure). The normal 

 fore femora, elongate thorax and abdomen, anteromedianly ridged 

 pronotum narrowed in the middle and expanded on the slightly 

 concave sides, and the medianly carinate propodeon, which, though 

 long, develops no definite " nucha," further characterise the genus 

 Stenomalus. In S. vmscarutn (Linn.) the legs are pale, yellowish, 

 or straw-coloured, only the last tarsal joints being dark. In the 

 male the fore and mid coxse are concolorous with the femora, etc., 

 only the hind coxae being dark and metallic. In the female all the 

 coxaj are dark, and the femora are occasionally a little smoky. 



