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Darwin Correspondence Project

From John William Douglas   20 February 1868

British Hemiptera. Heteroptera1

1 The sexes Different in colour or ornamentation.

1. Female paler than the male

Ex. Jalla dumosa, Lin. (See Hahn, Wanz. i, figs. 54 ♂, &

55 ♀.)

Systellonotus triguttatus, Lin. (See Brit. Hem. Pl. XII, fig.

2 & 2♀.)2

In this latter case the ♀ is decidedly less

conspicuous than the ♂. the former being without

elytra and paler brown body, the latter with conspicuous

marking on the elytra. (see also No 2 Head Difft. form)

Apocremnus ambiguus, Fall. ) male black

" obscurus, Kirscht. ) or dark:

Sthenarus Roseri, H Schf. ) female red

Capsus capillaris, Fab. ) or reddish.

Rhopatolomus ater, Lin.3 ) male black;

) pronotum4 of ♀ reddish.

( Zygonotus pselaphiformis, Westn.

( in the ♂, the elytra brown with markings See ( in the ♀ light brown without markings also ( difference ( 2 Female darker than the male— of ( Sphyrops ambulans, Fall. ) male brownish, form. ( Byrsoptera Caricis, Fall. )

( Myrmedobia coleoptrata, Fall. ) ♀ black.

( 3 Female varied

Zygonotus elegantulus Baerens.5 male elytra brown with

markings; ♀ apterous

pronotum red, body black

As a rule the sexes do not differ much in colour, the above are the chief exceptions.

I have not the material at hand to say anything special respecting the colour of exotics, but as far as I knw variation of it in the sexes is exceptional

2. The sexes different in size or form

As a general if not universal rule the ♀ is generally larger and more robust than the ♂; often, especially in Capsina and Anthocorina,6 the males have longer elytra than the females making the insects look larger than they are. In the genera Orthocephalus, Fieb., Bothynotus, Fieb. and in Sphyrops ambulans, Fall. Byrsoptera caricis, Fall., Myrmedobia coleoptrata, Fall. the ♀ looks remarkably different from the ♂, the body being very short and wide; and the elytra shorter still; in the last named the elytra fit close to the rounded abdomen like those of a beetle, Alexia pelifera. In Zygonotus elegantulus, Baerens., the ♂ has long elytra, brown with markings, the ♀ is apterous, pronotum bright red, abdomen short wide and black (See Brit. Hem. pl. xvi, fig. 1, 2, & 3, ♂ & ♀.7

3. Difference of structure of parts.

In addition to the difference in the elytra above mentioned may be noted

1 Form of head

Genus Globiceps—larger and more globose 2 Form of antennæ.—x2d joint thickened in ♀—

Genus Globiceps—especially in G. dispar, Boh. see Ent

Mag. iv, pl. 1 figs 4, ♂ & ♀.

Genus Heterocordylus—especially H. unicolor.

xx 2nd joint thickened in ♂—

Genus Apocremnus, Fieb.

Ex. A. ambiguus, Fall.

" A. obscurus, Kirschb.

xxx 2nd joint curved and remarkably produced at the apex, in ♂—in ♀ simple

Ex. Harpocera thoracica, Fall. (Brit. Hem. pl. 15, fig

3a)8 3 Form of tarsi.— In the genus Corixa, the monomerous tarsi

of the fore-legs in the ♂ are remarkably larger than in

the ♀, and though in all species cultrate, yet in each

is a modification of size and shape. (See Fiebers’ ‘Species


Musical powers— The faculty of stridulation occurs (as far as I know) only in the Homoptera and is confined to the males of the genus Cicada. There is but one species known in Britain— C. montana, Scop.,10 and the evidence of its musical powers is contradictory and therefore unsatisfactory. Of the foreign species, in this respect, I know nothing except by books. Nor, also, can I say, whether the curious appendages seen in exotic Homoptera are sexual or not, or are modified in the sexes. Nothing, as far as I know, has been observed of the courtship of the sexes in the Hemiptera.

The foregoing remarks as to difference of colour in the Heteroptera, speaking generally, will apply, I think to foreign species—though I doubt not there are as in our own Fauna, special exceptions, for which there seems to be no rule.

In the Homoptera (British) as far as I have observed, where the sexes differ, the ♀ is more obscure in colour than the ♂

Ex:— Delphax longipennis, Curt.— ♂ nearly black

with black-spotted legs—♀ ochraceous with

concolorous legs.

Acocephalus bifasciatus Lin.) in both the ♂

" albifrons Lin.11 ) is yellow with black

bands; the ♀

obscure brown not


In size the ♀ is larger than the ♂—

Sometimes the ♂ has long elytra & the ♀ short ones

Ex. Aræophus crassicornis Fab.12

JWD 20/2/68

CD annotations

1.1 Hemiptera. Heteroptera] underl blue crayon
1.3 Female paler] underl blue crayon
1.23 Female darker] underl blue crayon
2.1 As a rule … exceptions.] double scored blue crayon
4.1 general if not universal] underl blue crayon
4.1 larger] underl blue crayon
4.1 As a … ♀. 4.10] ‘I may pass over difference in shape of body, & Headadded blue crayon
4.8 apterous underl blue crayon
6.1 Musical … Hemiptera 6.7] crossed blue crayon
7.1 The foregoing … rule. 7.3] rule across page after paragraph
8.1 In the Homoptera] pointing hand, blue crayon
8.1 Homoptera] underl blue crayon
8.3 ♂ nearly black] underl blue crayon
8.7 ♀ obscure … banded. 8.8] underl blue crayon
Top of letter: ‘Douglasadded blue crayon
End of letter: ‘J. W. Douglas’ added ink


No letter from CD to Douglas has been found. Douglas had been mentioned by William Sweetland Dallas as an expert on British Hemiptera whom CD might contact for information on the proportion of the sexes and sexual characteristics (see letter from W. S. Dallas, 19 February 1868). Heteroptera is a suborder of Hemiptera (true bugs).
Douglas refers to Jalla dumosa (family Pentatomidae) in Hahn 1831–53; and to Systellonotus triguttatus (family Miridae) in Douglas and Scott 1865, a copy of which is in the Darwin Library–Down.
Apocremnus ambiguus (now recognised as a synonym of A. obscurus) is now Psallus ambiguus; Sthenarus roseri is now Salicarus roseri; Capsus capillaris is now Deraeocoris ruber; Rhopatolomus ater is now Capsis ater.
The pronotum is the dorsal part of the prothorax of an insect (OED).
Zygonotus pselaphiformis is now Loricula pselaphiformis; Sphyrops ambulans is now Mecomma ambulans; Byrsoptera caricis is now Cyrtorhinus caricis; Zygonotus elegantulus is now Loricula elegantulus.
Capsina and Anthocorina are taxa in the systematics of Heteroptera in Douglas and Scott 1865, pp. 27–37.
Byrsoptera carcis is now Orthonotus rufifrons. Male and female specimens of these species are described in Douglas and Scott 1865, pp. 349–50 (Sphyrops ambulans), pp. 352–54 (B. caricis), pp. 429–31 (Orthocephalus), pp. 484–5 (Myrmedobia coleoptrata), and pp. 488–90 and pl. 16 (Zygonotus elegantulus). ‘Alexia pelifera’ has not been identified.
Globiceps dispar is now Mecomma dispar. Douglas evidently refers to volume four of the Entomological Magazine; however no description of G. dispar has been found in this volume. Heterocordylus unicolor is a synonym of H. genistae. Apocremnus is now a subgenus of Psallus (family Miridae, plant bugs). Male and female antennae of Harpocera thoracica are figured in Douglas and Scott 1865, plate XV, figure 3a.
Corixa is in the family Corixidae. The reference is to Fieber 1852.
Cicada montana is now Melampsalta montana (the New Forest cicada), the only species native to Britain. The order Homoptera, though still widely referred to, is now invalid.
Delphax longipennis is now Stenocranus longipennis (family Delphacidae); Acocephalus is now Aphrodes (family Cicadellidae).
Douglas probably meant to write Aracopus crassicornis, which is now Delphax crassicornis.


Notes on sexual differences in British Hemiptera.

Letter details

Letter no.
John William Douglas
Charles Robert Darwin
Sent from
Source of text
DAR 81: 87
Physical description
AmemS 3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 5904,” accessed on 20 July 2019,

Also published in The Correspondence of Charles Darwin, vol. 16